merhaba arkadaşlar,
aşagıdaki aldıgım hatayı sizce neden veriyordur?

    function indir($embed)
    {
        $a = explode("URLX=",$embed); 
        $a = explode('"',$a[1]);
        $adres = url_decode($a[0]);
        $kaynak = file_get_contents($adres); 
        $a = explode("<VideoUrl1>",$kaynak); 
        $a = explode("</VideoUrl1>",$a[1]); 
        echo $a[0]; 
    }

functionu kullandıgım kod ise:

<object width="530" height="420"classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000"><param name="movie" value="http://services.akilli.tv/player3.swf?TYPE=2&amp;URLX=http://services.akilli.tv/xmlProviderv4/query.aspx?ACTION=video&amp;VDX=4061c9d2-6523-4f99-8bdc-de86d07fb6da"/><param name="bgcolor" value="#e7e7e7"/><param name="allowfullscreen" value="true"/><embed src="http://services.akilli.tv/player3.swf?TYPE=2&amp;URLX=http://services.akilli.tv/xmlProviderv4/query.aspx?ACTION=video&amp;VDX=4061c9d2-6523-4f99-8bdc-de86d07fb6da" type="application/x-shockwave-flash" bgcolor="#e7e7e7" width="530" height="420" allowfullscreen="true"/></object>

verdigi hata mesajı

Fatal error: Call to undefined function url_decode() in /var/www/vhosts/site.com/httpdocs/akilliconvert.php on line 19

19. satırda ise

$adres = url_decode($a[0]);