Inane ereg problem

My problem is this...to prevent users from running a bad search the below code checks for illegal characters, if it finds them...there is an error message with a display of illegal chars. The problem is the right square bracket. If I insert \] into the $excludeChars variable the rountine ceases to work...no error messages, it just won't find any errors in the sample text. Can someone explain why the right bracket is causing so much trouble. ken $excludeChars="\[\*\.\-\+\{\}\%\\$\|\#\@"; $text="when in t[he course of human events"; if(ereg("([$excludeChars])",$text)){ Print("bad characters\n"); $letters=implode(" ",explode("\\",$excludeChars)); print($letters); } else{ Print("ok to use"); }