<?php

$str = '
akwlhfwhfqwfh[2]
erhreherhreh
dsgdsgsdg[q]
';

$patterns = [
	'/(.*)\[2\]/',
	'/(.*)\[q\]/',
];
$replaces = [
	'<h2>$1</h2>',
	'<quote>$1</quote>',
];
echo preg_replace($patterns, $replaces, $str);