[MaryTheG(r)eek]

I don't think that:

$output = str_replace($find,$replace.$find, $output); 

is correct. You evaluate an expression there which maybe will cause endless loop by having $find there, which is also the first argument. I haven't seen all your code, but if you want to use that expression is better to add another variable before. eg:

$mynewreplace = $replace.$find;
$output = str_replace($find,$mynewreplace, $output); 

Maria