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                <?php declare(strict_types = 1);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                namespace Codor\Sniffs\Syntax;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use PHP_CodeSniffer_Sniff;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use PHP_CodeSniffer_File;  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                class NullCoalescingSniff implements PHP_CodeSniffer_Sniff  | 
            
            
                                                                        
                            
            
                                    
            
            
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                { | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Returns the token types that this sniff is interested in.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @return array  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function register(): array  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return [T_ISSET];  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Processes the tokens that this sniff is interested in.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param PHP_CodeSniffer_File $phpcsFile The file where the token was found.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param integer              $stackPtr  The position in the stack where  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     *                                    the token was found.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @return void  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function process(PHP_CodeSniffer_File $phpcsFile, $stackPtr)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $this->phpcsFile = $phpcsFile;  | 
            
                            
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                        $tokens          = $phpcsFile->getTokens();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $index           = $stackPtr;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        if ($this->couldBeNullCoalescing($tokens, $index)) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $phpcsFile->addError("Ternery found where Null Coalescing operator will work.", $stackPtr); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Determines if the current line has a ternary  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * operator that could be converted to a  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * null coalescing operator.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param  array   $tokens Tokens.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param  integer $index  Current index.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @return boolean  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected function couldBeNullCoalescing($tokens, $index): bool  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $questionMarkFound = false;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $semiColinFound = false;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        while (true) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            if ($tokens[$index]['type'] == 'T_SEMICOLON') { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                break;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            if ($tokens[$index]['type'] == 'T_INLINE_THEN') { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                $questionMarkFound = true;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            if ($tokens[$index]['type'] == 'T_INLINE_ELSE') { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                $semiColinFound = true;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $index++;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $questionMarkFound && $semiColinFound;  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                        
            
                                    
            
            
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                }  | 
            
            
                                                        
            
                                    
            
            
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In PHP it is possible to write to properties without declaring them. For example, the following is perfectly valid PHP code:
Generally, it is a good practice to explictly declare properties to avoid accidental typos and provide IDE auto-completion: