Id like to see if an aff code is there or not for a test, but with my C64 programmaing capabilities Im not getting there

Pls help...
http://refer.ccbill.com/cgi-bin/clic...y.com/test.php
This is in the test.php:
<?php
if (PA = = 0) {
echo "AFF CODE NOT THERE";
} else {
echo "AFF CODE THERE";
}
?>
It needs to print AFF CODE THERE when the &PA=999999 or so and if PA isnt there (zero) it needs to print AFF CODE NOT THERE. I know the = = have a space but otherwise the haha codes comes in...
Any 2 cents?
thanks!
Bob