I have a PHP page that queries a DB to populate a form for the user to modify the data and submit.
The query returns a number of rows which contain 3 items:

1. ImageID
2. ImageName
3. ImageDescription

The PHP page titles each box in the form with a generic name and appends the ImageID to it. Ie:

• ImageID_03
• ImageName_34
• ImageDescription_22

As it's unknown which images are going to have been retrieved from the DB then I can't know in advance what the name of the form entries will be. The form deals with a large number of entries at the same time.

My backend PHP form processor that gets the data just sees it as one big array:

[imageid_2] => 2
[imagename_2] => _MG_0214
[imageid_10] => 10
[imagename_10] => _MG_0419
[imageid_39] => 39
[imagename_39] => _MG_0420
[imageid_22] => 22
[imagename_22] => Curly Fern
[imagedescription_2] => Wibble
[imagedescription_10] => Wobble
[imagedescription_39] => Fred
[imagedescription_22] => Sally

I've tried to do an array walk on it to split it into 3 arrays which set places but am stuck:

// define empty arrays
$imageidarray = array();
$imagenamearray = array();
$imagedescriptionarray = array();

// our function to call when we walk through the posted items array
function assignvars($entry, $key)
{
 if (preg_match("/imageid/i", $key)) { 
  array_push($imageidarray, $entry);
 } elseif (preg_match("/imagename/i", $key)) {
//     echo " ImageName: $entry";
 } elseif (preg_match("/imagedescription/i", $key)) {
//     echo " ImageDescription: $entry";
 }
}

array_walk($_POST, 'assignvars');

This fails with the error:
array_push(): First argument should be an array in...

Am I approaching this wrong?