	<?php
	
	$html = "The quick brown fox jumps over the lazy dog";
	$replace = preg_replace('/\A(.*?)(brown fox)(.*?)\z/sim', '$1<span STYLE="font-size: x-large; color: #ffffff">$2</span>$3', $html);
	echo $replace;
	// The quick <span STYLE="font-size: x-large; color: #ffffff">brown fox</span> jumps over the lazy dog
