3v4l.org

run code in 500+ PHP versions simultaneously
<?php $content = '<table></table><p></p><table></table><p></p><table></table><p></p>'; $counter = 0; echo preg_replace_callback('~<table\K>~', function() use (&$counter) { return ' class="table_' . $counter++ . '">'; }, $content);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 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 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
<table class="table_0"></table><p></p><table class="table_1"></table><p></p><table class="table_2"></table><p></p>
preferences:
95.88 ms | 1951 KiB | 4 Q