Checkboxes, using a many to many relationship php

I am trying to create an admin form that allows users to select their requirements and save to a db using a many-to-many relationship.

I have been able to use a simple while loop to render the options for me:

while ($rows = $equipresults->fetch()) {
$eqid = $rows['req_id'];
$eqname = $rows['requirement'];
echo "
<label class='checkbox'>
<input type='checkbox' name='requirement[]' value='$eqid'> $eqname 
</label><br>
";}

I am trying to mark the check boxes as checked if the user has previously checked the control and saved to the db. I have created the below array using a RIGHT JOIN between the equipment table matching an my artist ID or IS NULL.

    Array ( 
[0] => Array ( [artistid] => 2 [req_id] => 1 [requirement] => Microphone ) 
[1] => Array ( [artistid] => [req_id] => 2 [requirement] => Table ) 
[2] => Array ( [artistid] => 2 [req_id] => 3 [requirement] => Chair ) 
[3] => Array ( [artistid] => [req_id] => 4 [requirement] => Microphone Stand ) 
[4] => Array ( [artistid] => [req_id] => 5 [requirement] => Personal Artifacts ) 
[5] => Array ( [artistid] => [req_id] => 6 [requirement] => Set Dressing ) 
[6] => Array ( [artistid] => [req_id] => 7 [requirement] => Raised Step )
[7] => Array ( [artistid] => [req_id] => 8 [requirement] => Other ) ) 

I have been playing about with a foreach loop, but I just can't manage to get the checkboxes to be checked.

$req=explode(",",$rows['requirement']);

if (!empty($equipresult)) {
    foreach ($equipresult as $row) {
      $checked = (in_array($row, $req)) ? 'checked="checked"' : '';
  ?>
            <label class='checkbox'>
                <input type="checkbox" name="requirement[]" value="<?php echo $row;?>"
                    <?php $checked;?>><?php echo implode(", ", $row);?>
            </label><br>
            <?php

}
}
?>

Ultimately I am trying to avoid hardcoding the html. Any guidance here would be really appreciated. I am also sure there is probably a really simple way of doing this