Simplified version

#include    <a_samp>
#include    <zcmd>

#define DIALOG_MUSIC 455
COMMAND:playtube(playerid,params[])
{
         ShowPlayerDialog(playerid,DIALOG_MUSIC,DIALOG_STYLE_INPUT,"PlayTube by iRaiDeN", "Please input the URL of the song you want (Example: wwww.youtube.com/watch?v=VID Change the VID!)","Play","Cancel");
return 1;
}


public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
        if(dialogid == DIALOG_MUSIC)
        {
                if(response)
                {
                if(strlen(inputtext))
                {
                if(strfind(inputtext,"www.youtube.com",true) == -1)
                {
                new localURL[128];
                strmid(localURL,inputtext,strfind(inputtext, "v=")+2,strfind(inputtext, "v=")+19);
                new localString[128];
                format(localString, 128, "http://mwrserver.com/youtube.php?videoid=%s",localURL);
                for(new i; i != MAX_PLAYERS; i++) PlayAudioStreamForPlayer(i,localString);
                }else{
                ShowPlayerDialog(playerid,DIALOG_MUSIC,DIALOG_STYLE_INPUT,"PlayTube by iRaiDeN", "Please input the URL of the song you want (Example: wwww.youtube.com/watch?v=VID Change the VID!)","Play","Cancel");
                }
                }else{
                ShowPlayerDialog(playerid,DIALOG_MUSIC,DIALOG_STYLE_INPUT,"PlayTube by iRaiDeN", "Please input the URL of the song you want (Example: wwww.youtube.com/watch?v=VID Change the VID!)","Play","Cancel");
                }
                }

        }
}