url encoding a mail to link in PHP

mailto_url_encode.php

<?php
$URL = "mailto:?subject=Is this a test message!";

    $url_var = $URL;
    //explode it and if it has a '?' it means it must have URL Parameters
    if(count($mail_split = explode('?', $URL))>1)
    {
        //if for some reason there's more than one '?' then we'll just add the exploded parts to the second part
        $mail_params = $mail_split[1];
        for($i=2; $i<count($mail_split); $i++)
        {
            $mail_params .= '?'.$mail_split[$i];
        }

        $final_mail_params = array();

        //break up the parameters into the $output array
        parse_str($mail_params, $output);
        foreach($output as $key => &$value)
        {
            //reform each key value pair but with a now url encoded value
            $final_mail_params[] = $key.'='.urlencode($value);
        }

        //make the string with all the key value pairs joined by &
        $final_mail_params_string = implode('&', $final_mail_params);
        
        //stick the original start of the mailto url back with the new encoded parameters
        $url_var = $mail_split[0].'?'.$final_mail_params_string;
    }
    
echo $url_var."\n";                
?>