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                <?php namespace Arcanedev\Units\Measures;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Arcanedev\Units\Bases\UnitMeasure;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Arcanedev\Units\Contracts\Measures\FileSize as FileSizeContract;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Arcanedev\Units\Traits\Calculatable;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * Class     FileSize  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @package  Arcanedev\Units\Measures  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @author   ARCANEDEV <[email protected]>  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                class FileSize extends UnitMeasure implements FileSizeContract  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Traits  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    use Calculatable;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Getters & Setters  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Get the default names.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return array  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             63                          | 
                
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                    public function defaultNames()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             63                          | 
                
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                        return array_combine(static::units(), [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             63                          | 
                
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                            'yotta',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'zetta',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'exa',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'peta',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'tera',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'gigabyte',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'megabyte',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'kilobyte',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'byte',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             21                          | 
                
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                        ]);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Constructor  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Distance constructor.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  float|int  $value  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  string     $unit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  array      $options  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                             66                          | 
                
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                    public function __construct($value = 0, $unit = self::B, array $options = [])  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    { | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $this->init($value, $unit, $options);  | 
            
            
                                                                        
                            
            
                                    
            
            
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                             66                          | 
                
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Main Methods  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Make a distance instance.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  float|int  $value  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  string     $unit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  array      $options  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return static  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public static function make($value = 0, $unit = self::B, array $options = [])  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return parent::make($value, $unit, $options);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Calculation Methods  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Add the file size.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  float|int  $value  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  string     $unit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return \Arcanedev\Units\Contracts\Measures\FileSize  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             6                          | 
                
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                    public function addSize($value, $unit = self::B)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             6                          | 
                
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                        return $this->add(static::make($value, $unit));  | 
            
                            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Sub the file size.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  float|int  $value  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  string     $unit  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return \Arcanedev\Units\Contracts\Measures\FileSize  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             6                          | 
                
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                    public function subSize($value, $unit = self::B)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             6                          | 
                
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                        return $this->sub(static::make($value, $unit));  | 
            
                            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /* -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     |  Other Methods  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     | -----------------------------------------------------------------  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Get all the distance ratios.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return array  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                    protected static function getRatios()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                        $rate   = 1024;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $ratios = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::YB => 0,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::ZB => 1,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::EB => 2,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::PB => 3,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::TB => 4,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::GB => 5,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::MB => 6,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::KB => 7,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             9                          | 
                
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                            FileSize::B  => 8,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                             3                          | 
                
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                        ];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    133
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                             9                          | 
                
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                        return array_map(function ($ratio) use ($rate) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    134
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                             9                          | 
                
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                            return static::calculate($rate, '^', $ratio);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    135
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                             9                          | 
                
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                        }, $ratios);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    137
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                }  | 
            
            
                                                        
            
                                    
            
            
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                    138
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.