problem of dynamic function

[zhengzhe_nb_zj]

I got an example of dynamic function,but when I invoke it ,an error appear as follows:
Fatal error: Call to undefined function: calculate() in F:\Apache\Apache2\htdocs\aa\function.php on line 111
I'm just seeking some guidance

[KoshNaranek]

Hmmmm... i can't find

function calculate(){
...
}

I'ts in the $header only... there is no php-command called 'calculate'... where is your function?

[zhengzhe_nb_zj]

I'am not very clear about the dynamic function.I think the function
named calculate in $header will work when call it.so it means dynamc function .am i right?I am not sure! help me please

[zhengzhe_nb_zj]

Oh!I know !I made a big mistake!I missed an "s" in the expression of "eval("eval($pared_function);".it should be "eval($parsed_function);" oK, it can work !but thank you all the same!