Script to move to next image - php

Question

I am writing a script to display images on my site. The images are stored on the server and the source (path) is on a mySQL database. I want to be able to move to the next (or previous picture) by invoking two php functions I have made to do so. The code I have written so far is:
<?php
require "db_connection.php";
$query="SELECT source FROM photos";
$result=mysql_query($query);
$count=0;
$numberofpics=mysql_num_rows($result);
$image=mysql_result($result, $count, "source");
$num=1;
function slideshowForward() {
$num=$num+1;
if($num==($numberofpics+1)) {
$num=1;
}
$count=$count+1;
$image=mysql_result($result, $count, "source");
}
function slideshowBack() {
$num=$num-1;
if ($num==0) {
$num=$numberofpics;
}
$count=$count-1;
$image=mysql_result($result, $count, "source");
}
?>
The html portion to display the images is:
<!-- FORWARD AND BACK FUNCTIONS-->
<a class="back" href="http://mywebsite.com/discoverandrank.php?function=slideshowBack()"> <img src="graphics/back.png"/></a>
<a class="next" href="http://mywebsite.com/discoverandrank.php? function=slideshowForward()"><img src="graphics/forward.png"/></a>
<!--DISPLAY MIDDLE PHOTO-->
<div id="thepics">
<img src="http://www.mywebsite.com/<?php echo $image; ?>" name="mypic" border=0 height="300" width="500"></img>
</div>
I'm pretty sure that the php script is incrementing/decrementing the count currently for the image, but I think the problem might be because the html (specifically img src="....") part is not re-evaluated when the count of the image increases?

Answer 1

Mmm there are two things to point out here:
I think that passing a function name as a parameter on an action is not a good idea, instead you should user something like: "http://mywebsite.com/discoverandrank.php?op=next&current=10" and then evaluate the op and current value to take some action.
For gettting the next picture from database you could use something like this:
"Select source FROM photos LIMIT "current+1" , 1"
For gettting the previous picture from database you could use something like this:
"Select source FROM photos LIMIT "current-1" , 1"
This way you dont need to keep counters and stuff, just have to check if those queries return any data.
Hope this helps!