Mingle Forum Guest Info allows you to enable guest posts to Mingle Forum without registration while still collecting contributor's email info. This version is an update from the original, outdated 1.0.1.

wpf-guestinfo.php

<?php
/*
Plugin Name: Mingle Forum Guest Info
Plugin URI: http://wpweaver.info/plugins/
Description: This is an add on to the Mingle Forum. It allows you allow geust posts without registration while requiring a name and e-mail to make posts easier to track.
Version: 1.0.2
Author: Bruce Wampler
Author URI: http://wpweaver.info
Text Domain: mingleforumguest
Copyright: 2009-2011, Bruce Wampler

GNU General Public License, Free Software Foundation <http://creativecommons.org/licenses/GPL/2.0/>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Versuib 1.0
*/

$wpw_guestID = 0;

// add the filters that will be called by Mingle Forum
add_filter('wpwf_guest_welcome_msg','wpf_guest_welcome_msg');
add_filter('wpwf_form_guestinfo','wpf_form_guestinfo');
add_filter('wpwf_quick_form_guestinfo','wpf_quick_form_guestinfo');
add_filter('wpwf_check_guestinfo','wpf_check_guestinfo');
add_filter('wpwf_change_userid','wpf_change_userid');
add_filter('wpwf_add_guest_sub', 'wpf_add_guest_sub');
add_filter('wpwf_new_posts','wpf_new_posts');

function wpf_guest_welcome_msg($value) {
    return "Welcome Guest. This forum allows guest posts without registration. However, please
        provide a name and a valid e-mail address (which will not be published). If you use the same
        e-mail address each time, you can subscribe to be notified when your post receives a reply.";
}

function wpf_change_userid($curID) {
    // override user ID if a guest has one now
    global $wpw_guestID;
    if ($wpw_guestID > 0) return $wpw_guestID;
    return $curID;
}

function wpf_new_posts($msg) {
    // to zap new posts line for guests
    //return $msg;
    return "";	// just hide for now
}


function wpf_check_guestinfo($unused) {
	/*
	 * We will be sure they filled in a user name and e-mail address, with optional web address.
	 * We will then see if the e-mail is already in the database, and use the info from there.
	 * If the e-mail is a new one, we will create a fake new user account, and fill it in with
	 * the information provided. This will provide an e-mail address to help track posters to the
	 * forum.
	 */
	global $wpw_guestID, $user_ID, $mingleforum;
	$gname 			= '';
	$gemail 		= '';
	$gurl 			= '';
	$err_msg 		= '';
	$msg 			= '';
	$err 			= false;
	$wpw_guestID 	= 0;

	if(isset($_POST['add_guest_name'])) {
		$gname = sanitize_text_field($_POST['add_guest_name']);
		sanitize_user($gname);

		if(strlen($gname) < 3) {
			$err_msg = '** You must provide a name or handle 3 or more letters long in order to post. Please use your browser back button.<br />';
			$err = true;
		}
	}
	else {
		$err_msg = '** You must provide a name or handle in order to post. Please use your browser back button.<br />';
		$err = true;
	}

	if(isset($_POST['add_guest_email'])) {
		$gemail = sanitize_text_field($_POST['add_guest_email']);
		if(!is_email($gemail)) {
			$err_msg .= '** You must provide a valid E-mail address in order to post. Please use your browser back button.<br />';
			$err = true;
		}
	}
	else {
		$err_msg .= '** You must provide a valid Email address in order to post. Please use your browser back button.<br />';
		$err = true;
	}

	$smsg = wpf_validate_guest($gname, $gemail); // check spammer lists
	if($smsg != '') {
		$err_msg = $smsg;
		$err = true;
	}

	if(isset($_POST['add_guest_web'])) { /* this copied from WP create user code */
		if(empty($_POST['add_guest_web']) || $_POST['add_guest_web'] == 'http://') {
			$gurl = '';
		}
		else {
			$gurl = esc_url_raw( $_POST['add_guest_web'] );
			$gurl = preg_match('/^(https?|ftps?|mailto|news|irc|gopher|nntp|feed|telnet):/is', $gurl) ? $gurl : 'http://'.$gurl;
		}
	}

	if($err) {
		$msg = "<h2>".__("An error occured", "mingleforum")."</h2>";
		$msg .= ("<div id='error'><p>".$err_msg."</p></div>");
		return $msg;            // fail, let caller handle error
	}

    // so no errors, so do a simple check of the other form fields before creating the guest user
    if (isset($_POST['add_topic_submit'])) {
	$subject = $mingleforum->input_filter($_POST['add_topic_subject']);
	$content = $mingleforum->input_filter($_POST['message']);
	if ($subject == "") return "";
	if ($content == "") return "";
    } elseif (isset($_POST['add_post_submit'])){
	$subject = $mingleforum->input_filter($_POST['add_post_subject']);
	$content = $mingleforum->input_filter($_POST['message']);
	if ($subject == "") return "";
	if ($content == "") return "";
    } else { return "";} // shouldn't get here!

    $options = get_option("mingleforum_options");
    if ($options['forum_captcha'] == true && !$user_ID) {	// have to duplicate the captcha check
	include_once(WPFPATH."captcha/shared.php");
	$wpf_code = wpf_str_decrypt($_POST['wpf_security_check']);
   	if(($wpf_code == $_POST['wpf_security_code']) && (!empty($wpf_code))) {
	    //It passed
  	} else {
	    $emsg = __("Security code does not match!", "mingleforum");
	    $msg = "<h2>".__("An error occured", "mingleforum")."</h2>";
            $msg .= "<div id='error'><p>".$emsg."</p></div>";
	    wp_die($msg);
	    //return $msg;            // fail, let caller handle error
	}
    }

    $existingID = email_exists($gemail);	// see if they've been here before! Email is the controlling entry
    if ($existingID) {
	$wpw_guestID = $existingID;
	$user_info = get_userdata($wpw_guestID);
	if ($gname != $user_info->display_name)		// Update display name
	    wp_update_user( array('ID'=>$wpw_guestID, 'display_name' => $gname, 'nickname' => $gname));
        if (!empty($gurl) && $gurl != $user_info->user_url) 	// let them change their website
	    wp_update_user( array('ID'=>$wpw_guestID, 'user_url' => $gurl));
    } else {
	// Create new fake account
	$added = false;
	while (!$added) {
	    $pw = wp_generate_password();	// generate a password
	    $ip = $_SERVER['REMOTE_ADDR'];
	    if ($ip == '') $ip = '0.0.0.0';
	    $userlogin = sanitize_user('G_'.wp_generate_password(8,false).'_'.$ip);	// and a login name
	    $wpw_guestID = wp_insert_user(array('user_pass'=>$pw, 'user_login'=>$userlogin, 'user_url' => $gurl,
			'first_name' => $gname, 'last_name' => 'Guest', 'display_name' => $gname, 'nickname' => $gname,
			'user_email' => $gemail));
	    if (!$wpw_guestID) continue;
	    $added = true;
	}
    }

    return "";
}

function wpf_form_guestinfo($unused) {
	global $user_ID;

	$name = '';
	$url = '';
	$email = '';

	$user_id = $user_ID;

	if($user_id != 0) {
		$user_info = get_userdata($user_id);
		$name = $user_info->display_name;
		$email = $user_info->user_email;
		$url = esc_url($user_info->user_url);
	}
	$out = '';

	$out .= "
	<tr>
		<td>" .  __("Name (required)", "mingleforum") . "</td>
		<td><input size='40%' type='text' name='add_guest_name' value='$name'></td>
	</tr>
	<tr>
		<td>" . __("Email (required, not published)", "mingleforum") . "</td>
		<td><input size='40%' type='email' name='add_guest_email' value='$email'></td>
	</tr>
	<tr>
		<td>" . __("Website (optional)", "mingleforum") . "</td>
		<td><input size='40%' type='url' name='add_guest_web' value='$url'></td>
	</tr>
	<tr>
		<td></td>
		<td><input type='checkbox' name='wpf_auto_sub' id='wpf_auto_sub'> " . __("Add this topic to your email notifications?", "mingleforum") . "</td>
	</tr>";
	return $out;
}
function wpf_quick_form_guestinfo($unused) {
	global $user_ID;

	$name = '';
	$url = '';
	$email = '';

	$user_id = $user_ID;

	if($user_id != 0) {
		$user_info = get_userdata($user_id);
		$name = $user_info->display_name;
		$email = $user_info->user_email;
		$url = esc_url($user_info->user_url);
	}
	$out = '';

	$out .= "
	<tr>
		<td>
			<input size='40%' type='text' name='add_guest_name' value='$name'> " . __("Name (required)", "mingleforum") . "<br>
			<input size='40%' type='email' name='add_guest_email' value='$email'> " . __("Email (required, not published)", "mingleforum") . "<br>
			<input size='40%' type='url' name='add_guest_web' value='$url'> " . __("Website (optional)", "mingleforum") . "<br>
			<input type='checkbox' name='wpf_auto_sub' id='wpf_auto_sub'> ". __("Add this topic to your email notifications?", "mingleforum") . "
		</td>
	</tr>";
	return $out;
}

function wpf_add_guest_sub($thread) {
	global $mingleforum;
	global $wpw_guestID;

	if(!isset($_POST['wpf_auto_sub']))
		return; // not asking to subscribe
	if($wpw_guestID < 1)
		return $thread;

	$id = $thread;
	$op = get_usermeta($wpw_guestID, 'wpf_useroptions');
	$topics = $op['notify_topics'];
	if(!is_array($topics))
		$topics = array();
	// Add topic
	if($mingleforum->array_search($id, $topics, TRUE))
		return; // this topic is already being followed

	$topics[] = $id;

	// Build array
	$op = array(
		'allow_profile' => $op['allow_profile'],
		'notify_topics' => (array)$topics
	);
	// Update meta
	update_user_meta($wpw_guestID, 'wpf_useroptions', $op);
}

function wpf_validate_guest($name,$email) {
	// run some validation checks on guest name - return '' if valid, error message otherwise
	if(function_exists('banhammer')) { // ban hammer installed, so use it!
		$errors = new WP_Error(); // need to call ban hammer
		banhammer($name, $email, $errors);

		if($errors->get_error_code())
			return 'Your name or email has been rejected because it was found on a spam list.';
	}
	return '';
}
?>