How can I add a field to the WordPress Register form? For example, I want to add the "First Name" field in the users profile to the Register form, but I can't figure out how to do that.
The field's name is first_name, but adding
<input type="text" name="first_name" id="first_name" value="<?php echo $_POST['first_name']; ?>" required="required" placeholder="<?php _e('First Name'); ?>" /> doesn't work for some reason. The form submits fine, but the profile doesn't get the "First Name" field filled in in the back end.
I'm editing this plugin to tweak the register form: http://wordpress.org/extend/plugins/s8-custom-login-and-registration/