Summary

When a mixed variable was narrowed to non-empty-array via array_key_exists() with a non-constant key, a subsequent array_key_exists() call on the same variable would report a false positive: "Parameter #2 $array of function array_key_exists expects array, non-empty-array given."

Changes

• Modified src/Type/Php/ArrayKeyExistsFunctionTypeSpecifyingExtension.php to include ArrayType(mixed, mixed) in the narrowing type when the variable is not already an array type
• Added regression test in tests/PHPStan/Rules/Functions/data/bug-14312.php and tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

Root cause

The ArrayKeyExistsFunctionTypeSpecifyingExtension narrowed non-constant key cases to a standalone NonEmptyArrayType accessory type. When intersected with mixed (the original type), the result was a standalone NonEmptyArrayType — an incomplete type that lacked the underlying ArrayType. This standalone accessory type was not recognized as a valid array subtype by ArrayType::accepts(), causing the false positive.

The fix conditionally includes ArrayType(mixed, mixed) in the narrowing type only when the variable is not already an array (to avoid interfering with existing key type refinements like subtracted types). This produces a proper array<mixed, mixed> & non-empty-array intersection type that is correctly accepted by array parameters.

Test

Added a rule test that verifies no error is reported when array_key_exists() is called on a variable already narrowed to non-empty-array by a prior array_key_exists() call.

Fixes phpstan/phpstan#14312