php preg_replace错误的字符集或编码

I've this simple code:

我有这个简单的代码：

function getCleanText($rawText) //removes doublespace and punctuation
{
    return strtolower(preg_replace("/[\s\t]+/u", " ", 
        preg_replace("/[^a-zA-Z1-9àèéìòù]+/u", " ", $rawText)));
}

echo getCleanText("uscì"). " uscì <br>";
function