Use extension_loaded() instead of checking for a constant

[cweagans]

https://github.com/phpseclib/mcrypt_compat/blob/master/lib/mcrypt.php#L44 should be if (!extension_loaded('mcrypt')) {

[terrafrost]

The concern I'd have with that is mcrypt_compat being loaded twice. phpseclib used to have issues with it being included twice:

phpseclib/phpseclib#217

random_compat works similarly to mcrypt_compat:

https://github.com/paragonie/random_compat/blob/master/lib/random.php

Mind you, whereas mcrypt_compat just does one if check before defining everything random_compat does if checks for everything.

[ivanweiler]

Hello all, I want to add check in legacy app, something like:

if(extension_loaded('mcrypt') || $hasMcryptCompat) {
//use mcrypt functions
} else {
//do something else
}

I can also use function_exists() ofc, but detecting mcrypt_compat would be better solution.
Anyway, maybe solution to both problems (how to detect mcrypt_compat, or not load it twice) would be to add something like
define('PHPSECLIB_MCRYPT_COMPAT', true) to mcrypt_compat ?

This way mcrypt_compat can detect if it's already loaded, it can use extension_loaded('mcrypt') and we can detect that we have it.

Just a suggestion, thx for great polyfill !!

[terrafrost]

phpseclib does three different tests in different places:

if (!defined('MCRYPT_MODE_ECB')) {
...
if (!function_exists('phpseclib_mcrypt_list_algorithms')) {
...
if (!function_exists('mcrypt_list_algorithms')) {

The only one that PHPSECLIB_MCRYPT_COMPAT would be a viable solution would be !function_exists('phpseclib_mcrypt_list_algorithms') and idk that it's any better than `PHPSECLIB_MCRYPT_COMPAT?

For your own check you could do !function_exists('phpseclib_mcrypt_list_algorithms') yourself?

[glensc]

I agree with @terrafrost here, that you should anyway test the feature (function exists, constant exists), not implementation details (extension_loaded, polyfill loaded). however, the loaded twice is not a real concern, why extension_loaded should not be used.