From Fedora Project Wiki
#!/usr/bin/php
<?
define('TAB_WIDTH', 5);

	foreach(file('php://stdin') as $l){
	preg_match_all('/\t+/', $l, $m, PREG_OFFSET_CAPTURE);
		foreach($m[0] as $mm){
		$l = str_replace(
			$mm[0]
			,str_repeat(' ', (TAB_WIDTH - ($mm[1] % TAB_WIDTH)) + (  TAB_WIDTH * ( strlen($mm[0]) - 1 )  ))
			, $l
		);
		}
	echo $l;
	}
?>