字符串翻转

function str_reverse($str){
    $r = array();
    $result = '';
    $encode = mb_detect_encoding($str, array('UTF8','GBK'));
    $len=mb_strlen($str, $encode);
    for($i=0;$i<$len;$i++){
        $r[] = mb_substr($str,$i,1,$encode);
    }
    while(($tmp = array_pop($r)) !== NULL){
        $result .= $tmp;
    }
    return $result;
}
echo str_reverse('360安全卫士');