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<?php $regex = '/(?:\h*C\h+|\G(?!^))\h*,*\h*\K\d+/i'; $strings = [ "C 1,13,7,2,55", "c 1 , 12,15 , 8 , 9,10,11", "1,2 , 4,5", "d 12456, 9890" ]; foreach ($strings as $s) { if (preg_match_all($regex, $s, $matches)) { print_r($matches[0]); } }
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.31, 8.3.0 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
Array ( [0] => 1 [1] => 13 [2] => 7 [3] => 2 [4] => 55 ) Array ( [0] => 1 [1] => 12 [2] => 15 [3] => 8 [4] => 9 [5] => 10 [6] => 11 )

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97.89 ms | 1297 KiB | 4 Q