argument.invalidConstant

Code example

<?php declare(strict_types = 1);

json_encode([], SORT_REGULAR);

Why is it reported?

The SORT_REGULAR constant is not a valid flag for the $flags parameter of json_encode(). Each PHP function that accepts predefined constants only works correctly with a specific set of them. Passing an unrelated constant results in unexpected behavior because the function interprets the underlying integer value differently than intended.

PHPStan maintains a map of allowed constants for parameters of built-in PHP functions and reports when a constant from a different domain is used.

This check is only performed on PHP 8.0+ because it relies on named argument support to accurately map arguments to parameters.

How to fix it

Use a constant that belongs to the correct function:

-json_encode([], SORT_REGULAR);
+json_encode([], JSON_PRETTY_PRINT);

Multiple valid constants can be combined with the | operator when the parameter accepts a bitmask:

-json_encode([], SORT_REGULAR);
+json_encode([], JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);