为什么在清理URL时会删除一些波斯语字符?

下面是我用来清理url的函数:

function make_clean_url($url){

    $url_word_separator = "-";

    // To replace new lines with space
    $url = preg_replace('/\n+/', " ", $url);

    // To replace spaces with -
    $url = preg_replace('/\s+/', "-", $url);

    // To replace dot(s) with -
    $url = preg_replace('/\.+/', "-", $url);

    // To remove html-entitis characters i.e «
    $url = preg_replace("/&#?[a-z0-9]+;/i","",$url);

    // To remove eveything except numbers, dash, number-sign, space and alphabet characters
    $url = preg_replace('/[^\x{600}-\x{6FF}a-zA-Z0-9 #\-]/u', '', $url); -- issue on this

    // To trim surrounded spaces and dashs
    $url = trim($url, " $url_word_separator");

    return $url;
}

这个regex也适用于大多数url。但是有一个例外:

echo make_clean_url("اﺻﻠﯽ ﺗﺮﯾﻦ ﻓﺮق اﺳﺘﻌﺎره ﻣﺼﺮﺣﻪ و ﻣﮑﻨﯿﻪ ﭼﯿﺴﺖ؟");
//=> ا--ق-اره--و--؟

Demo

\x{600}-\x{6FF} . 为什么要把它们移走?