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<?php $re = '/(?<=\w)(?=(?:\w\w)+$)/m'; $str = '121510'; preg_match_all($re, $str, $matches, PREG_SET_ORDER); // Print the entire match result var_dump($matches);
Output for 5.6.38, 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
array(2) { [0]=> array(1) { [0]=> string(0) "" } [1]=> array(1) { [0]=> string(0) "" } }

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178.79 ms | 403 KiB | 174 Q