PHP function showing blank screen? - php

Question

I am copying a youtube video tutorial for private messaging. The rest of the tutorial works fine, but as soon as I add this function to my site, my entire site goes blank and nothing is shown? No errors or anything, just a white screen? Have I done something wrong here? Here is the function:
<?php
function fetch_user_ids($usernames){
foreach ($usernames as &$name){
$name = mysql_real_escape_string($name);
}
$result = mysql_query("SELECT `userid`, `username` FROM `users` WHERE `username` IN ('" . implode("', '", $usernames) . "')");
$names = array();
while (($row = mysql_fetch_assoc($result)) !== false){
$names[$row['username']] = $row['userid'];
}
return $names;
}
?>
Here is the script to send the information:
<?php
if (isset($_POST['to'], $_POST['subject'], $_POST['body'])){
$errors = array();
if (empty($_POST['to'])){
$errors[] = 'You must enter atleast one name.';
}else if (preg_match('#^[a-z, ]+$#i', $_POST['to']) === 0){
$errors[] = 'The list of names you gave does not look valid.';
}else{
$usernames = explode(',', $_POST['to']);
foreach ($usernames as &$name){
$name = trim($name);
}
$user_ids = fetch_user_ids($usernames);
if (count($user_ids) !== count($usernames)){
$errors[] = 'The following users could not be found: ' . implode(', ', array_diff($usernames, array_keys($user_ids)));
}
}
if (empty($_POST['subject'])){
$errors[] = 'The subject cannot be empty';
}
if (empty($_POST['body'])){
$errors[] = 'You body must have some text!';
}
if (empty($errors)){
//Send message
}
}
if (isset($errors)){
if (empty($errors)){
echo '<div class="msg success">Your message has been sent ! return</div>';
}else{
foreach ($errors as $error){
echo '<div class="msg error">', $error, '</div>';
}
}
}
?>
<form action="" method="POST">
<div>
<label for="to">To</label>
<input type="text" name="to" id="to" />
</div>
<div>
<label for="subject">Subject</label>
<input type="text" name="subject" id="subject" />
</div>
<div>
<textarea name="body" rows="10" cols="110"></textarea>
</div>
<div>
<input type="submit" value="send" />
</div>
</form>
If I take away the "function" part, I can print the data, so it must be something to do with the function element?

Answer 1

I would suggest changing the !== to != and seeeing if that works, it could be interpreting it has a number and not as a bool

Answer 2

Make it simpler. Inside foreach, get rid of &$name and replace it with $name. Also check if your database is returning nothing.
foreach ($usernames as $name){
$name = mysql_real_escape_string($name);
}
$result = mysql_query("SELECT `userid`, `username` FROM `users` WHERE `username` IN ('" . implode("', '", $usernames) . "')");
// Check if the query itself is failing or not here:
if(!$result) die("Failed to perform query");
$names = array();
// Check if the database is returning any rows or not:
print_r(mysql_num_rows($result));
while($row = mysql_fetch_assoc($result)){
$names[$row['username']] = $row['userid'];
}
return $names;