rotate banner code help

[logicuk]

im using this banner rotate code but it dont seem to work with .swf's any ideas?

PHP Code:

$random_number = rand(1, 5);

$random_banner[1] = '<a href="http://www.site.com/" target="_blank"><img src="banners/sensi.gif" alt="" border="0" /></a>';
$random_banner[2] = '<a href="http://www.site2.com" target="_blank"><img src="banners/dna.gif" alt="" border="0" /></a>';
$random_banner[3] = '<a href="http://www.site3.com" target="_blank"><img src="banners/kiwi.gif" alt="" border="0" /></a>';
$random_banner[4] = '<a href="http://www.site4.com" target="_blank"><img src="banners/soft1.gif" alt="" border="0" /></a>';
$random_banner[5] = '<a href="http://www.site5.com" target="_blank"><img src="banners/banner.gif" alt="" border="0" /></a>';