- substr_count: documentation ( source)
- str_repeat: documentation ( source)
<?php
$haystack = "The <b>quick brown</b> fox jumps over the lazy dog
The <b>quick brown</b> fox jumps over the lazy dog
The <b>quick brown</b> fox jumps over the lazy dog";
$needle = "<b>quick brown</b>";
echo str_repeat($needle . "<br>", substr_count($haystack, $needle));