PHP dynamic call Method Instance code

The PHP dynamic call method example code is as follows:
<? Php
Require_once showErrMsg. php;
$ _ Action = (isset ($ _ REQUEST [action])? $ _ REQUEST [action]: "");
If ($ _ action! = Null & $ _ action! = ){
If (function_exists ($ _ action )){
Eval ("$ _ action ();");
} Else {
Die (showErrMsg ("<br> The method does not exist in the current PHP file [<B>". $ _ action. "() </B>]. "));
}
}
?>

<? Php
Function showErrMsg ($ strMsg ){
Return "<font color = red>". $ strMsg. "</font> ";
}
?>