Check if images exist, else null

Ok so how the images are stored are as follows:

Tables

Images:              |    Post2Images               |   Post:

ID      Filename |    Image_ID     Post_ID  |    ID     Name     Description

------------------------------------------------------------------------------------------

1       Image1     |     1                    1             |    1       Post1     This is description of post 1

2       Image2     |     2                    1             |

3      Image3      |     3                    1             |

------------------------------------------------------------------------------------------

4     Photo1        |    4                    2               |    2     Post2       This is description of post 2

5     Photo2        |    5                    2               |

So the above example is 2 different posts with Post 1 has 3 associated images, Post 2 has 2 associated images.

In my description I put placeholders [image1], [image2] ect. And with the origional post above I created an array with [image2] [image3] that will find those in the description field and replace those with variable $image2 and $image3 where those variables are as follows:

$photo_post = getPhotoPostByLinkname($Read, $_GET[post]);

$pix1 = getRelatedPhotos1($Read, $photo_post['post_id']);

$pix2 = getRelatedPhotos2($Read, $photo_post['post_id']);  

$pix3 = getRelatedPhotos3($Read, $photo_post['post_id']);

Where each function is as follows:

function getRelatedPhotos1($read, $post_id) {

$sql = "SELECTimages.photo_id, filename

   FROM images

   INNER JOIN Post2Images USING (image_id)

   WHERE post_id = $post_id

   LIMIT 0, 1";

return $read->fetchAll($sql);

}

And then:

<?php foreach ($pix2 as $picture2) { ?>

<?php foreach ($pix3 as $picture3) { ?>

<?php

$image2 = $picture2['filename'];

$image3 = $picture3['filename'];

I hope this will help explain my method and what I am trying to accomplish.