Fibonacci cass :/

<?php$str = (isset($_GET['str']) && $_GET['str'] != '') ? $_GET['str'] : '1';$rnd_max = 50;function loop($pos, $sstr) {	$tmp_str = '';	if(isset($sstr{$pos+1}) && $sstr{$pos+1} == $sstr{$pos}) {		if(isset($sstr{$pos+2}) && $sstr{$pos+2} == $sstr{$pos}) {			$tmp_str = '3'. $sstr{$pos};			if(isset($sstr{$pos+3})) $tmp_str .= loop($pos+3, $sstr);		} else {			$tmp_str = '2'. $sstr{$pos};			if(isset($sstr{$pos+2})) $tmp_str .= loop($pos+2, $sstr);		}	} else {		$tmp_str = '1'. $sstr{$pos};		if(isset($sstr{$pos+1})) $tmp_str .= loop($pos+1, $sstr);	}	return $tmp_str;}$time_pre_start = explode(' ', microtime());$time_start = $time_pre_start[1] + $time_pre_start[0];for($rnd = 0; $rnd < $rnd_max; $rnd++) {	$len = strlen($str);	$str = loop(0, $str);	echo $rnd .' : '. $str .'<br />';}$time_pre_end = explode(' ', microtime());$time_end = $time_pre_end[1] + $time_pre_end[0];$time = $time_end - $time_start;echo $time .' secondes !';?>