What's the difference between WordPress defined function random_int() and PHP built-in function random_int()?

Also, if there is a difference, how does the PHP interpreter understand which of the two functions I'm calling?

1 Answer 1


WordPress is old. In fact, it is older than PHP7, in which PHP introduced random_int(). WP wanted/needed this functionality before, so another method was implemented.

how does the PHP interpreter understand which of the two functions I'm calling?

Good question. The interpreter doesn't understand this. And hence, if you had PHP7 and would define this function new, you would get an error. This is why. the file with the function definition is only loaded, when random_int() is not available by default.

wp-includes/random_compat/random.php lines 212-214 are

if (!function_exists('random_int')) {
    require_once $RandomCompatDIR.'/random_int.php';
  • So if your server is PHP7 and PHP's own random_int() is callable, this one is used and the file never included.

  • If your server is not PHP7 or PHP's own random_int() is not callable for any reasons, the file is included and another implementation will be given.

This is done, so WordPress can run on different systems. Those with PHP5 and those with PHP7.

How is it different? I can't really speak to it. The files WP uses seem to be from this random_compat repository, which is also linked from the PHP doc (and suggested if you don't have PHP's own implementation available).

One quick difference that I already saw: PHP's random_int() tries to use getrandom(2) on Linux machines, while the compat random_int() only uses /dev/urandom.

When in doubt, I would use the system's versions (PHP) instead of those introduced by software (WP). But that is only my opinion.

  • "When in doubt, I would use the system's versions" It sounds like you explain at the start of your answer that you can't choose. Either it's already in there (PHP >= 7) and WP won't load it, or it's not there so WP will load it. Is there a middle ground where you pick yourself (disabling WP's function explicitly, I presume)? Sure, you can make any modification you want. But is it worth it to go non-standard in what seems like a relatively core function?
    – Mast
    Aug 28, 2018 at 18:19
  • @Mast There's always a way. You could load that repository and simply change the function names (random_int_custom() eg) for it to be usable. The last comment was rather meant as a: it makes sense that it works this way (rather using system functions than your own), and I wouldn't recommend going the extra miles to circumvent this
    – kero
    Aug 29, 2018 at 10:10
  • 1
    You don't recommend going the extra miles, ok. That's all I wanted to know :-)
    – Mast
    Aug 29, 2018 at 10:23

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