how to loop and compare two arrays at the same time(PHP) - php

Question

I have two array. What I want to do is compare the key ['user_id'] of two arrays, if they are the same, pass the ['user_id'] and ['ref'] in hidden form. I tried to put them into two foreach, but system seems into a dead lock.
<?php foreach($_SESSION['printing_set'] as $data) { ?>
<?php foreach(getProvenaMailableUserlist() as $userlist){ ?>
<input type="hidden" name="reference[<?php echo $data['user_id'] ?>]" value="<? if($userlist['user_id'] == $data['user_id']){echo $userlist['ref'];} ?>" />
<?php } ?>
<?php } ?>
What is the right way to do that?

Answer 1

What you are doing is printing again and again the part of '<input type="hidden" name="...'. here is what you should do
<?php
echo '<input type="hidden" name="reference[' . $data['user_id'] . ']" value="'; //olny one time.
foreach($_SESSION['printing_set'] as $data) {
foreach(getProvenaMailableUserlist() as $userlist){
if($userlist['user_id'] == $data['user_id']){
echo $userlist['ref']; //only if condition is true
}
}
}
echo '" />'; //only one time
?>

Answer 2

You've got some funky formatting going on, so it's hard to tell where the error might be. Try it like this:
<?php
foreach($_SESSION['printing_set'] as $data) {
foreach(getProvenaMailableUserlist() as $userlist){
$value = "";
if($userlist['user_id'] == $data['user_id'])
$value = $userlist['ref'];
echo "<input type='hidden' name='reference$user_id' value='$value' /> \n";
}
}
?>