I agree with two of the posts in this thread. Either use a straight
<a href="abc.php?image=xxx"><img src="xxx.jpg" alt="Click for a bigger image"></a>
or you could do some Javascript:
<img src="xxx.jpg" alt="Click for a bigger image" onmouseup="window.location='abc.php?image=xxx'">
Has to be onmouseup, onclick is no good in NN4.
Then your php script would take the passed parameter $image and work out which file to display.