Complex classes like Packer often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use Packer, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 18 | class Packer  | 
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| 19 | { | 
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| 20 | private const UTF8_REGEX = '/\A(?:  | 
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| 21 | [\x00-\x7F]++ # ASCII  | 
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| 22 | | [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte  | 
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| 23 | | \xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs  | 
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| 24 |         | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}  # straight 3-byte | 
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| 25 | | \xED[\x80-\x9F][\x80-\xBF] # excluding surrogates  | 
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| 26 |         |  \xF0[\x90-\xBF][\x80-\xBF]{2}     # planes 1-3 | 
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| 27 |         | [\xF1-\xF3][\x80-\xBF]{3}          # planes 4-15 | 
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| 28 |         |  \xF4[\x80-\x8F][\x80-\xBF]{2}     # plane 16 | 
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| 29 | )*+\z/x';  | 
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| 30 | |||
| 31 | private $isDetectStrBin;  | 
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| 32 | private $isForceStr;  | 
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| 33 | private $isDetectArrMap;  | 
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| 34 | private $isForceArr;  | 
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| 35 | private $isForceFloat32;  | 
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| 36 | |||
| 37 | /**  | 
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| 38 | * @var Packable[]|null  | 
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| 39 | */  | 
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| 40 | private $transformers;  | 
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| 41 | |||
| 42 | /**  | 
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| 43 | * @param PackOptions|int|null $options  | 
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| 44 | *  | 
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| 45 | * @throws InvalidOptionException  | 
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| 46 | */  | 
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| 47 | 182 | public function __construct($options = null)  | 
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| 48 |     { | 
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| 49 | 182 |         if (null === $options) { | 
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| 50 | 181 | $options = PackOptions::fromDefaults();  | 
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| 51 | 20 |         } elseif (!$options instanceof PackOptions) { | 
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| 52 | 20 | $options = PackOptions::fromBitmask($options);  | 
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| 53 | }  | 
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| 54 | |||
| 55 | 182 | $this->isDetectStrBin = $options->isDetectStrBinMode();  | 
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| 56 | 182 | $this->isForceStr = $options->isForceStrMode();  | 
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| 57 | 182 | $this->isDetectArrMap = $options->isDetectArrMapMode();  | 
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| 58 | 182 | $this->isForceArr = $options->isForceArrMode();  | 
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| 59 | 182 | $this->isForceFloat32 = $options->isForceFloat32Mode();  | 
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| 60 | 182 | }  | 
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| 61 | |||
| 62 | 2 | public function registerTransformer(Packable $transformer) : self  | 
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| 63 |     { | 
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| 64 | 2 | $this->transformers[] = $transformer;  | 
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| 65 | |||
| 66 | 2 | return $this;  | 
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| 67 | }  | 
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| 68 | |||
| 69 | 114 | public function pack($value)  | 
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| 70 |     { | 
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| 71 | 114 |         if (\is_int($value)) { | 
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| 72 | 63 | return $this->packInt($value);  | 
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| 73 | }  | 
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| 74 | 74 |         if (\is_string($value)) { | 
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| 75 | 35 |             if ($this->isForceStr) { | 
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| 76 | 3 | return $this->packStr($value);  | 
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| 77 | }  | 
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| 78 | 32 |             if ($this->isDetectStrBin) { | 
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| 79 | 29 | return \preg_match(self::UTF8_REGEX, $value)  | 
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| 80 | 22 | ? $this->packStr($value)  | 
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| 81 | 29 | : $this->packBin($value);  | 
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| 82 | }  | 
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| 83 | |||
| 84 | 3 | return $this->packBin($value);  | 
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| 85 | }  | 
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| 86 | 51 |         if (\is_array($value)) { | 
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| 87 | 28 |             if ($this->isDetectArrMap) { | 
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| 88 | 21 | return \array_values($value) === $value  | 
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| 89 | 12 | ? $this->packArray($value)  | 
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| 90 | 21 | : $this->packMap($value);  | 
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| 91 | }  | 
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| 92 | |||
| 93 | 7 | return $this->isForceArr ? $this->packArray($value) : $this->packMap($value);  | 
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| 94 | }  | 
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| 95 | 29 |         if (null === $value) { | 
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| 96 | 5 | return "\xc0";  | 
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| 97 | }  | 
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| 98 | 28 |         if (\is_bool($value)) { | 
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| 99 | 10 | return $value ? "\xc3" : "\xc2";  | 
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| 100 | }  | 
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| 101 | 20 |         if (\is_float($value)) { | 
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| 102 | 6 | return $this->packFloat($value);  | 
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| 103 | }  | 
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| 104 | 14 |         if ($value instanceof Ext) { | 
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| 105 | 10 | return $this->packExt($value->type, $value->data);  | 
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| 106 | }  | 
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| 107 | 4 |         if ($this->transformers) { | 
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| 108 | 2 |             foreach ($this->transformers as $transformer) { | 
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| 109 | 2 |                 if (null !== $packed = $transformer->pack($this, $value)) { | 
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| 110 | 2 | return $packed;  | 
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| 111 | }  | 
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| 112 | }  | 
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| 113 | }  | 
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| 114 | |||
| 115 | 3 | throw PackingFailedException::unsupportedType($value);  | 
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| 116 | }  | 
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| 117 | |||
| 118 | 1 | public function packNil()  | 
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| 119 |     { | 
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| 120 | 1 | return "\xc0";  | 
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| 121 | }  | 
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| 122 | |||
| 123 | 2 | public function packBool($bool)  | 
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| 127 | |||
| 128 | 98 | public function packInt($int)  | 
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| 129 |     { | 
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| 130 | 98 |         if ($int >= 0) { | 
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| 131 | 66 |             if ($int <= 0x7f) { | 
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| 132 | 40 | return \chr($int);  | 
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| 133 | }  | 
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| 134 | 34 |             if ($int <= 0xff) { | 
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| 135 | 12 | return "\xcc".\chr($int);  | 
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| 136 | }  | 
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| 137 | 26 |             if ($int <= 0xffff) { | 
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| 138 | 12 | return "\xcd".\chr($int >> 8).\chr($int);  | 
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| 139 | }  | 
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| 140 | 16 |             if ($int <= 0xffffffff) { | 
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| 141 | 10 |                 return \pack('CN', 0xce, $int); | 
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| 142 | }  | 
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| 143 | |||
| 144 | 8 |             return \pack('CJ', 0xcf, $int); | 
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| 145 | }  | 
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| 146 | |||
| 147 | 34 |         if ($int >= -0x20) { | 
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| 148 | 8 | return \chr(0xe0 | $int);  | 
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| 149 | }  | 
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| 150 | 26 |         if ($int >= -0x80) { | 
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| 151 | 6 | return "\xd0".\chr($int);  | 
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| 152 | }  | 
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| 153 | 20 |         if ($int >= -0x8000) { | 
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| 154 | 6 | return "\xd1".\chr($int >> 8).\chr($int);  | 
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| 155 | }  | 
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| 156 | 14 |         if ($int >= -0x80000000) { | 
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| 157 | 6 |             return \pack('CN', 0xd2, $int); | 
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| 158 | }  | 
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| 159 | |||
| 160 | 8 |         return \pack('CJ', 0xd3, $int); | 
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| 161 | }  | 
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| 162 | |||
| 163 | 9 | public function packFloat($float)  | 
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| 164 |     { | 
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| 165 | 9 | return $this->isForceFloat32  | 
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| 166 | 1 |             ? "\xca".\pack('G', $float) | 
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| 167 | 9 |             : "\xcb".\pack('E', $float); | 
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| 168 | }  | 
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| 169 | |||
| 170 | 39 | public function packStr($str)  | 
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| 171 |     { | 
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| 172 | 39 | $length = \strlen($str);  | 
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| 173 | |||
| 174 | 39 |         if ($length < 32) { | 
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| 175 | 25 | return \chr(0xa0 | $length).$str;  | 
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| 176 | }  | 
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| 177 | 14 |         if ($length <= 0xff) { | 
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| 178 | 8 | return "\xd9".\chr($length).$str;  | 
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| 179 | }  | 
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| 180 | 6 |         if ($length <= 0xffff) { | 
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| 181 | 4 | return "\xda".\chr($length >> 8).\chr($length).$str;  | 
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| 182 | }  | 
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| 183 | |||
| 184 | 2 |         return \pack('CN', 0xdb, $length).$str; | 
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| 185 | }  | 
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| 186 | |||
| 187 | 21 | public function packBin($str)  | 
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| 188 |     { | 
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| 189 | 21 | $length = \strlen($str);  | 
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| 190 | |||
| 191 | 21 |         if ($length <= 0xff) { | 
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| 192 | 17 | return "\xc4".\chr($length).$str;  | 
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| 193 | }  | 
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| 194 | 4 |         if ($length <= 0xffff) { | 
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| 195 | 2 | return "\xc5".\chr($length >> 8).\chr($length).$str;  | 
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| 196 | }  | 
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| 197 | |||
| 198 | 2 |         return \pack('CN', 0xc6, $length).$str; | 
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| 199 | }  | 
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| 200 | |||
| 201 | 20 | public function packArray(array $array)  | 
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| 202 |     { | 
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| 203 | 20 | $data = $this->packArrayHeader(\count($array));  | 
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| 204 | |||
| 205 | 20 |         foreach ($array as $val) { | 
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| 206 | 18 | $data .= $this->pack($val);  | 
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| 207 | }  | 
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| 208 | |||
| 209 | 20 | return $data;  | 
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| 210 | }  | 
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| 211 | |||
| 212 | 20 | public function packArrayHeader($size)  | 
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| 213 |     { | 
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| 214 | 20 |         if ($size <= 0xf) { | 
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| 215 | 14 | return \chr(0x90 | $size);  | 
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| 216 | }  | 
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| 217 | 6 |         if ($size <= 0xffff) { | 
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| 218 | 4 | return "\xdc".\chr($size >> 8).\chr($size);  | 
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| 219 | }  | 
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| 220 | |||
| 221 | 2 |         return \pack('CN', 0xdd, $size); | 
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| 222 | }  | 
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| 223 | |||
| 224 | 24 | public function packMap(array $map)  | 
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| 255 | |||
| 256 | 24 | public function packMapHeader($size)  | 
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| 257 |     { | 
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| 258 | 24 |         if ($size <= 0xf) { | 
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| 259 | 18 | return \chr(0x80 | $size);  | 
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| 260 | }  | 
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| 261 | 6 |         if ($size <= 0xffff) { | 
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| 262 | 4 | return "\xde".\chr($size >> 8).\chr($size);  | 
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| 263 | }  | 
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| 267 | |||
| 268 | 18 | public function packExt($type, $data)  | 
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| 289 | }  | 
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| 290 | 
According to the PSR-2, the body of a case statement must start on the line immediately following the case statement.
}
To learn more about the PSR-2 coding standard, please refer to the PHP-Fig.