php算法-找到数组中字符串最左最长的字符串

$arr = ['aaabb','aac','aad'];
	echo findLeftStr($arr);
	function findLeftStr($arr){
		$tmpArr = [];
		foreach($arr as $v){
			$tmpArr[strlen($v)] = $v;
		}
		$minStr = $tmpArr[min(array_keys($tmpArr))];
		$minLen = strlen($minStr);
		for($i = 0;$i<$minLen;$i++){
			foreach($arr as $v){
				if($v[$i] != $minStr[$i]){
					break 2;
				}
			}
		}
		
		$returnStr = '';
		if($i > 0){
			$returnStr = substr($minStr, 0,$i);
		}
		return $returnStr;
	}