3v4l.org

run code in 300+ PHP versions simultaneously
<?php $text = <<<TEXT >num, blah, blah, blah ATCGACTGAATCGA >num, blah, blah, blah ATCGATCGATCGATCG >num, blah, blah, blah ATCGATCGATCGATCG TEXT; echo preg_replace_callback( "~^>\Knum~m", function () { static $counter = 0; return ++$counter; }, $text );
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
>1, blah, blah, blah ATCGACTGAATCGA >2, blah, blah, blah ATCGATCGATCGATCG >3, blah, blah, blah ATCGATCGATCGATCG
preferences:
127.86 ms | 407 KiB | 5 Q