Complex classes like Reader 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 Reader, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 50 | class Reader extends AbstractCsv implements Countable, IteratorAggregate, JsonSerializable  | 
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| 51 | { | 
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| 52 | /**  | 
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| 53 | * header offset.  | 
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| 54 | *  | 
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| 55 | * @var int|null  | 
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| 56 | */  | 
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| 57 | protected $header_offset;  | 
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| 58 | |||
| 59 | /**  | 
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| 60 | * header record.  | 
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| 61 | *  | 
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| 62 | * @var string[]  | 
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| 63 | */  | 
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| 64 | protected $header = [];  | 
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| 65 | |||
| 66 | /**  | 
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| 67 | * records count.  | 
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| 68 | *  | 
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| 69 | * @var int  | 
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| 70 | */  | 
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| 71 | protected $nb_records = -1;  | 
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| 72 | |||
| 73 | /**  | 
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| 74 |      * {@inheritdoc} | 
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| 75 | */  | 
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| 76 | protected $stream_filter_mode = STREAM_FILTER_READ;  | 
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| 77 | |||
| 78 | /**  | 
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| 79 |      * {@inheritdoc} | 
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| 80 | */  | 
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| 81 | 3 | public static function createFromPath(string $path, string $open_mode = 'r', $context = null)  | 
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| 82 |     { | 
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| 83 | 3 | return parent::createFromPath($path, $open_mode, $context);  | 
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| 84 | }  | 
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| 85 | |||
| 86 | /**  | 
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| 87 |      * {@inheritdoc} | 
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| 88 | */  | 
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| 89 | 27 | protected function resetProperties()  | 
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| 90 |     { | 
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| 91 | 27 | parent::resetProperties();  | 
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| 92 | 27 | $this->nb_records = -1;  | 
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| 93 | 27 | $this->header = [];  | 
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| 94 | 27 | }  | 
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| 95 | |||
| 96 | /**  | 
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| 97 | * Returns the header offset.  | 
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| 98 | *  | 
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| 99 | * If no CSV header offset is set this method MUST return null  | 
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| 100 | *  | 
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| 101 | * @return int|null  | 
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| 102 | */  | 
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| 103 | 15 | public function getHeaderOffset()  | 
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| 104 |     { | 
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| 105 | 15 | return $this->header_offset;  | 
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| 106 | }  | 
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| 107 | |||
| 108 | /**  | 
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| 109 | * Returns the CSV record used as header.  | 
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| 110 | *  | 
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| 111 | * The returned header is represented as an array of string values  | 
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| 112 | *  | 
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| 113 | * @return string[]  | 
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| 114 | */  | 
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| 115 | 21 | public function getHeader(): array  | 
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| 116 |     { | 
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| 117 | 21 |         if (null === $this->header_offset) { | 
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| 118 | 15 | return $this->header;  | 
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| 119 | }  | 
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| 120 | |||
| 121 | 9 |         if ([] !== $this->header) { | 
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| 122 | 3 | return $this->header;  | 
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| 123 | }  | 
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| 124 | |||
| 125 | 9 | $this->header = $this->setHeader($this->header_offset);  | 
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| 126 | |||
| 127 | 6 | return $this->header;  | 
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| 128 | }  | 
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| 129 | |||
| 130 | /**  | 
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| 131 | * Determine the CSV record header.  | 
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| 132 | *  | 
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| 133 | * @throws Exception If the header offset is set and no record is found or is the empty array  | 
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| 134 | *  | 
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| 135 | * @return string[]  | 
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| 136 | */  | 
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| 137 | 12 | protected function setHeader(int $offset): array  | 
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| 138 |     { | 
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| 139 | 12 | $header = $this->seekRow($offset);  | 
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| 140 | 12 |         if (false === $header || [] === $header) { | 
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| 141 | 6 |             throw new Exception(sprintf('The header record does not exist or is empty at offset: `%s`', $offset)); | 
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| 142 | }  | 
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| 143 | |||
| 144 | 6 |         if (0 === $offset) { | 
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| 145 | 3 | return $this->removeBOM($header, mb_strlen($this->getInputBOM()), $this->enclosure);  | 
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| 146 | }  | 
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| 147 | |||
| 148 | 3 | return $header;  | 
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| 149 | }  | 
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| 150 | |||
| 151 | /**  | 
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| 152 | * Returns the row at a given offset.  | 
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| 153 | *  | 
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| 154 | * @return array|false  | 
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| 155 | */  | 
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| 156 | 12 | protected function seekRow(int $offset)  | 
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| 157 |     { | 
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| 158 | 12 |         foreach ($this->getDocument() as $index => $record) { | 
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| 159 | 12 |             if ($offset === $index) { | 
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| 160 | 9 | return $record;  | 
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| 161 | }  | 
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| 162 | }  | 
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| 163 | |||
| 164 | 9 | return false;  | 
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| 165 | }  | 
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| 166 | |||
| 167 | /**  | 
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| 168 | * Returns the document as an Iterator.  | 
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| 169 | */  | 
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| 170 | 18 | protected function getDocument(): Iterator  | 
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| 171 |     { | 
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| 172 | 18 |         if (70400 > PHP_VERSION_ID && '' === $this->escape) { | 
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| 173 | 6 | $this->document->setCsvControl($this->delimiter, $this->enclosure);  | 
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| 174 | |||
| 175 | 6 | return EmptyEscapeParser::parse($this->document);  | 
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| 176 | }  | 
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| 177 | |||
| 178 | 12 | $this->document->setFlags(SplFileObject::READ_CSV | SplFileObject::READ_AHEAD | SplFileObject::SKIP_EMPTY);  | 
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| 179 | 12 | $this->document->setCsvControl($this->delimiter, $this->enclosure, $this->escape);  | 
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| 180 | 12 | $this->document->rewind();  | 
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| 181 | |||
| 182 | 12 | return $this->document;  | 
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| 183 | }  | 
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| 184 | |||
| 185 | /**  | 
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| 186 | * Strip the BOM sequence from a record.  | 
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| 187 | *  | 
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| 188 | * @param string[] $record  | 
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| 189 | *  | 
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| 190 | * @return string[]  | 
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| 191 | */  | 
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| 192 | 12 | protected function removeBOM(array $record, int $bom_length, string $enclosure): array  | 
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| 193 |     { | 
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| 194 | 12 |         if (0 === $bom_length) { | 
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| 195 | 3 | return $record;  | 
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| 196 | }  | 
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| 197 | |||
| 198 | 9 | $record[0] = mb_substr($record[0], $bom_length);  | 
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| 199 | 9 |         if ($enclosure.$enclosure != substr($record[0].$record[0], strlen($record[0]) - 1, 2)) { | 
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| 200 | 6 | return $record;  | 
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| 201 | }  | 
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| 202 | |||
| 203 | 3 | $record[0] = substr($record[0], 1, -1);  | 
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| 204 | |||
| 205 | 3 | return $record;  | 
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| 206 | }  | 
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| 207 | |||
| 208 | /**  | 
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| 209 |      * {@inheritdoc} | 
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| 210 | */  | 
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| 211 | 9 | public function __call($method, array $arguments)  | 
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| 212 |     { | 
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| 213 | 9 | static $whitelisted = ['fetchColumn' => 1, 'fetchOne' => 1, 'fetchPairs' => 1];  | 
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| 214 | 9 |         if (isset($whitelisted[$method])) { | 
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| 215 | 3 | return (new ResultSet($this->getRecords(), $this->getHeader()))->$method(...$arguments);  | 
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| 216 | }  | 
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| 217 | |||
| 218 | 6 |         throw new BadMethodCallException(sprintf('%s::%s() method does not exist', static::class, $method)); | 
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| 219 | }  | 
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| 220 | |||
| 221 | /**  | 
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| 222 |      * {@inheritdoc} | 
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| 223 | */  | 
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| 224 | 3 | public function count(): int  | 
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| 225 |     { | 
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| 226 | 3 |         if (-1 === $this->nb_records) { | 
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| 227 | 3 | $this->nb_records = iterator_count($this->getRecords());  | 
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| 228 | }  | 
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| 229 | |||
| 230 | 3 | return $this->nb_records;  | 
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| 231 | }  | 
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| 232 | |||
| 233 | /**  | 
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| 234 |      * {@inheritdoc} | 
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| 235 | */  | 
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| 236 | 6 | public function getIterator(): Iterator  | 
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| 237 |     { | 
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| 238 | 6 | return $this->getRecords();  | 
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| 239 | }  | 
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| 240 | |||
| 241 | /**  | 
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| 242 |      * {@inheritdoc} | 
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| 243 | */  | 
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| 244 | 3 | public function jsonSerialize(): array  | 
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| 245 |     { | 
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| 246 | 3 | return iterator_to_array($this->getRecords(), false);  | 
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| 247 | }  | 
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| 248 | |||
| 249 | /**  | 
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| 250 | * Returns the CSV records as an iterator object.  | 
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| 251 | *  | 
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| 252 | * Each CSV record is represented as a simple array containing strings or null values.  | 
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| 253 | *  | 
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| 254 | * If the CSV document has a header record then each record is combined  | 
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| 255 | * to the header record and the header record is removed from the iterator.  | 
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| 256 | *  | 
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| 257 | * If the CSV document is inconsistent. Missing record fields are  | 
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| 258 | * filled with null values while extra record fields are strip from  | 
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| 259 | * the returned object.  | 
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| 260 | *  | 
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| 261 | * @param string[] $header an optional header to use instead of the CSV document header  | 
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| 262 | */  | 
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| 263 | 21 | public function getRecords(array $header = []): Iterator  | 
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| 264 |     { | 
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| 265 | 21 | $header = $this->computeHeader($header);  | 
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| 266 | 18 |         $normalized = static function ($record): bool { | 
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| 267 | 18 | return is_array($record) && $record != [null];  | 
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| 268 | 18 | };  | 
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| 269 | |||
| 270 | 18 | $bom = '';  | 
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| 271 | 18 |         if ($this->is_input_bom_skipped) { | 
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| 272 | 15 | $bom = $this->getInputBOM();  | 
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| 273 | }  | 
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| 274 | |||
| 275 | 18 | $document = $this->getDocument();  | 
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| 276 | 18 | $records = $this->stripBOM(new CallbackFilterIterator($document, $normalized), $bom);  | 
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| 277 | 18 |         if (null !== $this->header_offset) { | 
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| 278 | 6 |             $records = new CallbackFilterIterator($records, function (array $record, int $offset): bool { | 
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| 279 | 6 | return $offset !== $this->header_offset;  | 
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| 280 | 6 | });  | 
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| 281 | }  | 
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| 282 | |||
| 283 | 18 | return $this->combineHeader($records, $header);  | 
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| 284 | }  | 
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| 285 | |||
| 286 | /**  | 
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| 287 | * Returns the header to be used for iteration.  | 
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| 288 | *  | 
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| 289 | * @param string[] $header  | 
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| 290 | *  | 
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| 291 | * @throws Exception If the header contains non unique column name  | 
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| 292 | *  | 
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| 293 | * @return string[]  | 
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| 294 | */  | 
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| 295 | 27 | protected function computeHeader(array $header)  | 
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| 307 | |||
| 308 | /**  | 
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| 309 | * Combine the CSV header to each record if present.  | 
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| 310 | *  | 
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| 311 | * @param string[] $header  | 
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| 312 | */  | 
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| 313 | 33 | protected function combineHeader(Iterator $iterator, array $header): Iterator  | 
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| 330 | |||
| 331 | /**  | 
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| 332 | * Strip the BOM sequence from the returned records if necessary.  | 
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| 333 | */  | 
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| 334 | 27 | protected function stripBOM(Iterator $iterator, string $bom): Iterator  | 
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| 351 | |||
| 352 | /**  | 
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| 353 | * Selects the record to be used as the CSV header.  | 
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| 354 | *  | 
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| 355 | * Because the header is represented as an array, to be valid  | 
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| 356 | * a header MUST contain only unique string value.  | 
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| 357 | *  | 
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| 358 | * @param int|null $offset the header record offset  | 
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| 359 | *  | 
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| 360 | * @throws Exception if the offset is a negative integer  | 
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| 361 | *  | 
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| 362 | * @return static  | 
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| 363 | */  | 
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| 364 | 24 | public function setHeaderOffset($offset): self  | 
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| 383 | }  | 
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| 384 |