PHP Regex / PCRE - Regex pattern Caching?

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PHP

regular-expression

I am trying to build a PHP/REGEX Benchmarking tool. Basically so I can compare the processing time of a regular expression to the processing time of a potentially updated regex.

The problem is, the first time I run the test- lets say it gives me a .005 time.. the second time it runs it is .0008 - obviously the regex is being cached somewhere. I would like to clear this cache out and after several days of googling I have no other recourse but to post here!

Anyone have a clue how to force the preg_match to treat each "test" as an entirely new test? I've tried clearing the session, expiring the session, I've tried running a loop of 10000 randomly generated regex tests but still, no matter what I've done, if I test the same one twice- the second time is ALWAYS faster, without any changes at all.

Thanks for reading, I look forward to input/feedback! If you are to propose a different solution, please just keep in mind that I am using PHP RegEx and the technology does have to be PHP unfortunately.

Cheers!
Dan

<?php
session_start();
try {
	if (strtoupper($_SERVER['REQUEST_METHOD']) == 'POST') {
			clearstatcache();
			$starttime = -microtime(true);
			$subject = $_POST['subject'];
			$pattern = $_POST['regex'];
			$pattern = str_replace(array("\n", "\r"), ' ', $pattern);
			preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 0);
			echo "Error Level: ", preg_last_error(), "\r\n";
			echo "Sample Size (num characters): ", strlen($subject), "\r\n";
			echo "Regex: ", $pattern, "\r\n";
			echo "Matches: ", count($matches), "\r\n";
			$starttime += microtime(true);
			echo "Execution Time:", sprintf('%f', $starttime), "\r\n-----------------------------\r\n";
			print_r($matches);
	}
} catch (Exception $e) {
    echo "Caught exception: ",  $e->getMessage(), "\r\n";
}

session_destroy();	
?>