Enabling PHP PCRE case insensitive searching for specific sections of your regular expression.

test.php

<?php
$testExpression = '/(?i)te(?-i)st/';

testPCRESectionOnly($testExpression,'test');
testPCRESectionOnly($testExpression,'TEst');
testPCRESectionOnly($testExpression,'teST');
testPCRESectionOnly($testExpression,'TEST');

/*
Should return:
Match
Match
No match
No match

More information here: http://www.regular-expressions.info/modifiers.html
*/

function testPCRESectionOnly($regExp,$testString) {

	if (preg_match($regExp,$testString)) {
		echo("Match\n");
		return;
	}

	echo("No match\n");
}