How to turn this into automatic?

In the following code, please have to select a radio button and then press OK.

How can this be made so that when pressing OK it is automaticly selected as the value of beeing checked?

      echo "<div class='content'>";
echo "<form action=\"subscription.php\" method=\"post\" name=\"sub_form\"".($popup ? " target=\"formPopup\"" : "")." onsubmit=\"submitform();false;\">
 		<input type=\"text\" size=\"".($popup ? "15" : "15")."\" name=\"email_addr\" value=\"".translate("EMAIL_ADDRESS")."\" onfocus=\"if (this.value=='".translate("EMAIL_ADDRESS")."') this.value=''\" />
&nbsp;<input type=\"button\" name=\"sub\" value=\" OK \" onclick=\"submitform()\" /><br />\n
    <input type=\"radio\" class='radio' name=\"op\" value=\"join" ;

  if(!$conf->sub_validation) echo "_direct";
  echo "\" checked=\"checked\" /> ".translate("NEWSLETTER_SUBSCRIPTION")."\n";
  echo "\t\t<input type=\"radio\" class='radio' name=\"op\" value=\"leave";
  if(!$conf->unsub_validation) echo "_direct";
  echo "\" /> ".translate("NEWSLETTER_UNSUBSCRIPTION");

PHP:

 

I am not sure what you want. It seems you already have chosen one as default.