<?php

header('Content-Type: text/plain; charset=urf-8');

$count = null;
for ( $i = 0; $i < 10000; $i++ )
{
	$start = microtime(true);
	
	$str = 'if (!preg_match(#^[A-Za-z_]+$#, $text)) { ';
	
	/*if (!preg_match('#^[A-Za-z_]+$#', $str))
	{
		// has bad characters
		$str = $str;
	}*/
	
	$str = preg_replace('/[^a-z_]/i', '', $str); // remove the "i" if you don't want A-Z to be matched as well
	//$str = preg_replace('/[^a-zA-Z_]/', '', $str);
	$count[] = 10*(microtime(true)-$start);
}

echo 'String: ' . $str . "\n";
echo 'Average: ' . (array_sum($count)/count($count)) . "\n";
//echo 'Time taken: ' . ($end - $start);

?>