URLs with numbers after tld do not pass

Can someone help me modify the following function to allow referral strings in the URLs? This is a URL checker on a directory script

IT will take URLS like www.mysite.com/?r=candy

but not

www.mysite.com/?r=13345

why would the alphas validate but not the numbers

here is the function

    function is_url($urladdr)
    { 
        $regexp = "^(https?://)";  // http:// 
        $regexp .= "?(([0-9a-z_!~*'().&=+$%-]+:)?[0-9a-z_!~*'().&=+$%-]+@)?";  // username:password@ 
        $regexp .= "(([0-9]{1,3}\.){3}[0-9]{1,3}";  // IP- 199.194.52.184 
        $regexp .= "|";  // allows either IP or domain 
        $regexp .= "([0-9a-z_!~*'()-]+\.)*"; // tertiary domain(s)- www. 
        $regexp .= "([0-9a-z][0-9a-z-]{0,61})?[0-9a-z]\."; // second level domain 
        $regexp .= "[a-z]{2,6})"; // first level domain- .com or .museum 
        $regexp .= "(:[0-9]{1,4})?"; // port number- :80 
        $regexp .= "((/?)|"; // a slash isn't required if there is no file name 
        $regexp .= "(/[0-9a-z_!~*'().;?:@&=+$,%#-]+)+/?)$"; // filename/queries/anchors 
        
        //qualified domain 
        if (eregi( $regexp, $urladdr ))
        { 
            // No http:// at the front? lets add it. 
            if (!eregi( "^https?://", $urladdr )) $urladdr = "http://" . $urladdr; 
        
            // If it's a plain domain or IP there should be a / on the end 
            if (!eregi( "^https?://.+/", $urladdr )) $urladdr .= "/"; 
        
            // If it's a directory on the end we should add the proper slash 
            // We should first make sure it isn't a file, query, or fragment 
            if ((eregi( "/[0-9a-z~_-]+$", $urladdr)) && (!eregi( "[\?;&=+\$,#]", $urladdr))) $urladdr .= "/"; 
            return ($urladdr); 
        } 
        else 
            return false; // The domain didn't pass the expression 
    
    }

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