[php-src] Issue #7778: Enum could not be converted to string with \array_intersect

Issue: https://github.com/php/php-src/issues/7778 Author: benelori ### Description The following code: ```php <?php class EnumTest extends Unit { public function testArrayIntersect(): void { $array1 = [TestEnum::TEST]; $array2 = [TestEnum::TEST]; $actual = \array_intersect($array1, $array2); self::assertCount(1, $actual); } } enum TestEnum { case TEST; } ``` Resulted in this output: ``` Object of class TestEnum could not be converted to string ``` But I expected this output instead: ``` I expected the test to pass and internally \array_intersect to be able to work with enums. The same goes for \array_diff as well, so most probably other array functions, too ``` ### PHP Version PHP 8.1.0 ### Operating System php:8.1-fpm-buster