Webusers registering other users

<?php
/* 
 * Register another user
 *
 * Last modified: TS 3/4/2009
 *
 * INPUTS (required): 
 *	&formTpl 	- form to display
 *	&namePrefix 	- all input element names should be prefixed with this string to avoid collisions with any other web user snippets
 *	&groups		- group to add user to
 *				(Warning - only partially implemented: 1. Currently only accepts one group! 2. OnBeforeAddToGroup not triggered)
 */
 
$namePrefix_len = strlen($namePrefix);

$form_chunk = $modx->getChunk($formTpl);

// Has form been submitted? Check for $_POST[&namePrefix*] and build $NewUser array.
// ---------------------------------------------------------------------------------
foreach ($_POST as $param_name => $param_value)
	{
	if (substr($param_name, 0, $namePrefix_len) == $namePrefix)
		{
		$form_submitted = true;
		$NewUser[substr($param_name, $namePrefix_len)] = get_magic_quotes_gpc() ? stripslashes($param_value) : $param_value;
		}
	}
	
if ($form_submitted)
	{	
	// Form validation
	// ---------------
	$errmsgs = null;
	$result = mysql_query('SELECT username FROM '.$modx->getFullTableName('web_users')." WHERE username = '{$NewUser['username']}'");
	if ($result && mysql_num_rows($result))
		$errmsgs['username'] = '<p class="error">Username already in use</p>';
	if (!eregi('^[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.([a-zA-Z]{2,4})$', $NewUser['email']))
		$errmsgs['email'] = '<p class="error">Email address invalid</p>';
		
	if ($errmsgs)
		{
		// Failed validation - get Form template and parse it.
		// ---------------------------------------------------
		foreach($errmsgs as $msg_name => $errmsg) $form_chunk = str_replace("[+errmsg.{$msg_name}+]", $errmsg, $form_chunk);
		foreach($_POST as $param_name => $param_value) $form_chunk = str_replace("[+post.{$param_name}+]", html_sanitise_data($param_value), $form_chunk);
		}
		
	else
		{
		// Validation successful
		// ---------------------
		
		// Generate password
		//        0    5    0    5    0    5    0
		$chars = 'abcdefghjkmnpqrstuvwxyz23456789'; 
 		$i = 8; 
 		$NewUser['password'] = '';
		while ($i--) $NewUser['password'] .= substr($chars, rand() % 30, 1);

		// Trigger event
		$modx->invokeEvent('OnBeforeWebSaveUser', array('Attributes'=>$NewUser)); // untested

		// Insert into MODx database
		$result = mysql_query('INSERT INTO '.$modx->getFullTableName('web_users')." (username, password) VALUES ('{$NewUser['username']}', '".md5($NewUser['password']).'\')');
		if ($result)
			{
			$result = mysql_query('INSERT INTO '.$modx->getFullTableName('web_user_attributes').' (internalKey, fullname, email) VALUES ('.($NewUser['internalKey'] = mysql_insert_id()).", '{$NewUser['fullname']}', '{$NewUser['email']}')");
		
			// If successful add to web groups
			if ($result)
				{
				$result = mysql_query('INSERT INTO '.$modx->getFullTableName('web_groups').' (webgroup, webuser)
								VALUES ((SELECT id FROM '.$modx->getFullTableName('webgroup_names')." WHERE name = '{$groups}'), {$NewUser['internalKey']})");

				// If successful trigger event and send email to user
				if ($result)
					{
					$modx->invokeEvent('OnWebSaveUser', array('mode'=>'new', 'user'=>$NewUser));
					mail($NewUser['email'], $modx->config['emailsubject'],
						str_replace('[+pwd+]', $NewUser['password'],
							str_replace('[+ufn+]', $NewUser['fullname'],
								str_replace('[+uid+]', $NewUser['username'],
									str_replace('[+sname+]', $modx->config['site_name'],
										str_replace('[+semail+]', $modx->config['emailsender'],
											str_replace('[+surl+]', $modx->config['site_url'], $modx->config['websignupemail_message'])))))),
												'Content-Type: text/plain; charset="'.$modx->config['modx_charset']."\"\r\nFrom: ".$modx->config['emailsender']);
					}
				}
			}
			
		if (!$result) return '<p class="error">Internal Error - please try again later</p>'; // !! Early return !!
		else
			{
			// Remove placeholders from form
			$form_chunk = preg_replace('/\[\+(errmsg|post)\.[^+]+\+\]/i', '', $form_chunk);
			} 
		}
	}
	
return $form_chunk;
?>

<div id="register-pupil">
	<form action="[~[*id*]~]" method="post">
		<div class="text">
			<label for="pupil_email">Pupil's email</label>
			<input id="pupil_email" type="text" name="pupil_email" value="[+post.pupil_email+]" />
			[+errmsg.email+]
		</div>
		<div class="text">
			<label for="pupil_username">Desired user name</label>
			<input id="pupil_username" type="text" name="pupil_username" value="[+post.pupil_username+]" />
			[+errmsg.username+]
		</div>
		<div class="text">
			<label for="pupil_fullname">Pupil's full name</label>
			<input id="pupil_fullname" type="text" name="pupil_fullname" value="[+post.pupil_fullname+]" />
		</div>
		<div class="submit">
			<input class="button" type="submit" value="Add Pupil" />
		</div>
	</form>
</div>