php mb_detect_encoding判断字符串编码方法

$encode = mb_detect_encoding($q, array('GB2312','GBK','UTF-8'));
echo $encode."
";
if($encode=="GB2312")
{
    $q = iconv("GBK","UTF-8",$q);
}
else if($encode=="GBK")
{
    $q = iconv("GBK","UTF-8",$q);
}
else if($encode=="EUC-CN")
{
    $q = iconv("GBK","UTF-8",$q);
}
else//CP936
{
    //$q = iconv("GB2312","UTF-8",$q);
}

// 使用 iconv 转换并判断是否等值，效率不高
function is_utf8 ($str) {
    if ($str === iconv('UTF-8', 'UTF-8//IGNORE', $str)) {
        return 'UTF-8';
    }
}
// 多种编码的情况
function detect_encoding ($str) {
    foreach (array('GBK', 'UTF-8') as $v) {
        if ($str === iconv($v, $v . '//IGNORE', $str)) {
            return $v;
        }
    }
}

$encode = mb_detect_encoding($keytitle, array('ASCII','GB2312′,'GBK’,'UTF-8');