PHP - Warning: Implode() [function.implode]: Invalid Arguments Passed

My error is 'Warning: implode() [function.implode]: Invalid arguments passed in /home/definiti/public_html/contact.php on line 73'

Im not sure how to fix this error, as I looked online and it says that my implode() has the right layout too it..

Line 73 in my code (I took the HTML code out) is this line;

Code: [Select]
$message = implode("<br>\n", $messages);

My whole code is;

Code: [Select]
<?php
# PHP Copyright 2007, Thomas Boutell and Boutell.Com, Inc.
# Edited by Definition Designs.

$recipient = 'defenitiondesigns@googlemail.com';
$serverName = 'www.definition-designs.co.uk';


if ($_POST['send']) {
sendMail();
} elseif (($_POST['cancel']) || ($_POST['continue'])) {
redirect();
} else {
displayForm(false);
}

function displayForm($messages)
{
global $login;
$escapedEmail = htmlspecialchars($_POST['email']);
$escapedRealName = htmlspecialchars($_POST['realname']);
$escapedSubject = htmlspecialchars($_POST['subject']);
$escapedBody = htmlspecialchars($_POST['body']);
$returnUrl = $_POST['returnurl'];
if (!strlen($returnUrl)) {
$returnUrl = $_SERVER['HTTP_REFERER'];
if (!strlen($returnUrl)) {
$returnUrl = '/';
}
}
$escapedReturnUrl = htmlspecialchars($returnUrl);
?>


<?php
    
if (count($messages) > 0) {
$message = implode("<br>\n", $messages);
echo("<h4>$message</h4>\n");
}
?>

<form method="POST" action="<?php echo $_SERVER['DOCUMENT_URL']?>">
<p>
<b>Your</b> Email Address   
<input
name="email"
size="35"
maxlength="35"
value="<?php echo $escapedEmail?>"/>
</p>
<p>
Your <b>Real</b> Name   
<input
name="realname"
size="35"
maxlength="35"
value="<?php echo $escapedRealName?>"/>

</p>
<p>
Subject Of Your Message   
<input
name="subject"
size="35"
maxlength="35"
value="<?php echo $escapedSubject?>"/>

</p>
<p>
<i>Please enter the text of your message in the field that follows.</i>
</p>
<textarea
name="body"
rows="10"
cols="60"><?php echo $escapedBody?></textarea>
<p>
<input type="submit" name="send" value="Send Your Message"/>
<input type="submit" name="cancel" value="Cancel - Never Mind"/>
</p>
<input
type="hidden"
name="returnurl"
value="<?php echo $escapedReturnUrl?>"/>
</form>

<?php
}

function redirect()
{
global $serverName;
$returnUrl = $_POST['returnurl'];
$prefix = "http://$serverName/";
if (!beginsWith($returnUrl, $prefix)) {
$returnUrl = "http://$serverName/"; 
}
header("Location: $returnUrl");
}

function beginsWith($s, $prefix)
{
return (substr($s, 0, strlen($prefix)) === $prefix);
}

function sendMail()
{
global $recipient;

$messages = array();

$email = $_POST['email'];
if (!preg_match("/^[\w\+\-\.\~]+\@[\-\w\.\!]+$/", $email)) {
$messages[] = "That is not a valid email address. In format: You@something.com";
}
$realName = $_POST['realname'];
if (!preg_match("/^[\w\ \+\-\'\"]+$/", $realName)) {
$messages[] = "The real name field must contain only alphanumeric characters, spaces and + or - signs.";
}
$subject = $_POST['subject'];
if (preg_match('/^\s*$/', $subject)) {
$messages[] = "Please specify a subject for your message.


";
}
$body = $_POST['body'];
        if (preg_match('/^\s*$/', $body)) {
$messages[] = "Your message was blank. Fill out a message or Click Cancel to cancel message.";
}
   if (count($messages)) {
displayForm($messages);
return;
}

mail($recipient, 
 $subject, 
 $body) or die("unable to send the mail!");
 
$escapedReturnUrl = htmlspecialchars($_POST['returnurl']);
?>

<form method="POST" action="<?php echo $_SERVER['DOCUMENT_URL']?>">
<input type="submit" name="continue" value="Click Here To Continue"/>
<input
type="hidden"
name="returnurl"
value="<?php echo $escapedReturnUrl?>"/>
</form>

<?php
}
?>