enumerators and enum_exists function are available in php version greater or equal to 8.1

Author: ioigoume

src/JsonMapper.php

@@ -300,7 +300,7 @@ public function map($json, $object)
                 && is_a($type, 'Traversable', true)
             ) {
                 $array = $this->createInstance($type, false, $jvalue);
-            } else if (enum_exists($type)) {
+            } else if (PHP_VERSION_ID >= 80100 && enum_exists($type)) {
                 $evalue = $type::tryFrom($jvalue);
                 if ($evalue === null) {
                     throw new JsonMapper_Exception(

tests/Enums_PHP81_Test.php

@@ -38,6 +38,10 @@ public function testEnumMapping()
      */
     public function testBackedEnumPropertyIsMappedFromString(): void
     {
+        if (PHP_VERSION_ID < 80100) {
+            $this->markTestSkipped('Enumerators are not supported for PHP versions below 8.1');
+        }
+
         $json = (object) [
             'stringBackedEnum' => 'foo',
             'intBackedEnum' => 2,
@@ -60,6 +64,10 @@ public function testBackedEnumPropertyIsMappedFromString(): void
      */
     public function testBackedEnumPropertyWithInvalidStringThrowsJsonMapperException(): void
     {
+        if (PHP_VERSION_ID < 80100) {
+            $this->markTestSkipped('Enumerators are not supported for PHP versions below 8.1');
+        }
+
         $json = (object) [
             'stringBackedEnum' => 'not-a-valid-enum-value',
             'intBackedEnum' => 'not-a-valid-enum-value',