Question

My code is like this:

<?php
define("ERROR", "SOMETHING WRONG WITH MY DATABASE");
... 
if (!mysql_query($q)){
  die(ERROR);
}
?>

Now I want to replace “SOMETHING WRONG WITH MY DATABASE” with mysql_error() in case I want to debug it. what is the easiest way ?

This does not seem to work work: define("ERROR", mysql_error());

—- edit —

I don’t want to use mysql_error() under production environment, it may help the attacker figure out something related to my database? That’s my point of using a constant string

as in C you can do
#define x yourfunction()
I’m not sure if I can do the same in php

Answer 1

The simple answer is “you cannot do that”. The whole point of constant is that it’s constant as in its value is never changed. If it refers to a function call, the function can return any value – and it’s not constant any more.

One trick you can do is define the function call itself to be the value of the constant – and then eval it on demand, something like this:

define("ERROR", "return mysql_error()");
...
die(eval(ERROR));

However this is really a rather bad code. You’d be much better off doing

die(mysql_error());