Question

Has anyone encountered this?

var_dump(CRYPT_SHA256 == 1); // returns bool(true)
var_dump(defined(CRYPT_SHA256)); // returns bool(false)

Answer 1

Add quotation marks

defined('CRYPT_SHA256')

Otherwise, you are asking whether the value of the CRYPT_SHA256 constant is also the name of another constant….

defined(CRYPT_SHA256) === defined('1');

Edit : Add namespace

If your constant is defined in a namespace, you must include it in the constant name.

namespace Some\Namespace;

const MY_CONST = 'value';

var_dump( defined('MY_CONST') ); // false unless another constant has been defined
var_dump( defined('Some\Namespace\MY_CONST'); // true

This is not the case in the original question, but it can be a cause of the same problem too.