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 );

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24.27 ms | 404 KiB | 5 Q