3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = '<p>"bla" bla</p>'; echo preg_replace( '~<p>\W*\K\w~', '<span class="first_letter">$0</span>', $str );
Output for 8.0.1 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
<p>"<span class="first_letter">b</span>la" bla</p>
preferences:
66.35 ms | 402 KiB | 91 Q