Try

Author: VincentLanglet

conf/config.neon

@@ -1541,11 +1541,6 @@ services:
 		tags:
 			- phpstan.broker.dynamicFunctionReturnTypeExtension
 
-	-
-		class: PHPStan\Type\Php\GetenvFunctionReturnTypeExtension
-		tags:
-			- phpstan.broker.dynamicFunctionReturnTypeExtension
-
 	-
 		class: PHPStan\Type\Php\GetParentClassDynamicFunctionReturnTypeExtension
 		tags:

resources/functionMap_php80delta.php

@@ -78,8 +78,10 @@
 		'imagejpeg' => ['bool', 'im'=>'GdImage', 'filename='=>'string|resource|null', 'quality='=>'int'],
 		'imagerotate' => ['false|object', 'src_im'=>'resource', 'angle'=>'float', 'bgdcolor'=>'int', 'ignoretransparent='=>'int'],
 		'imagescale' => ['false|object', 'im'=>'resource', 'new_width'=>'int', 'new_height='=>'int', 'method='=>'int'],
-		'getenv' => ['array<string, string>|string|false', 'varname'=>'string|null', 'local_only='=>'bool'],
-		'getenv\'1' => ['array<string, string>'],
+		'getenv' => ['array<string, string>', 'varname'=>'null', 'local_only='=>'bool'],
+		'getenv\'1' => ['string|false', 'varname'=>'string', 'local_only='=>'bool'],
+		'getenv\'2' => ['array<string, string>|string|false', 'varname'=>'string|null', 'local_only='=>'bool'],
+		'getenv\'3' => ['array<string, string>'],
 		'ldap_set_rebind_proc' => ['bool', 'ldap'=>'resource', 'callback'=>'?callable'],
 		'mb_decode_numericentity' => ['string|false', 'string'=>'string', 'convmap'=>'array', 'encoding='=>'string'],
 		'mb_encoding_aliases' => ['list<non-falsy-string>', 'encoding'=>'string'],