php按照指定长度截取字符串的代码

php按照指定长度截取字符串的代码，如果字符串超出了指定的长度，会用...替换，不过这段代码不支持中英文的区分

<?php
//if a string is longer than the defined length, 
//it will add 3 periods to the end of the string.
//you can change it to what ever you want for example:
//return substr($str,0,$len).'[<a href="read_more.html">Read More</a>]';
//http://www.sharejs.com
function strLength($str,$len){
    $lenght = strlen($str);
    if($lenght > $len){
        return substr($str,0,$len).'...';
    }else{
        return $str;
    }
}
$str = "This is a fairly long string.";
//The fist part is the string, the second part is how long it can be
echo strLength($str,10).'<br>';
echo strLength($str,30);
?>