diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a09c56d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/.idea
diff --git a/composer.json b/composer.json
index a0b6f39..36d0f97 100644
--- a/composer.json
+++ b/composer.json
@@ -1,28 +1,28 @@
-{
-    "name": "simplesurance/paypal-rest-api-sdk-php",
-    "description": "PayPal's PHP SDK for REST APIs",
-    "keywords": ["paypal", "payments", "rest", "sdk"],
-    "type": "library",
-    "license": "Apache-2.0",
-    "homepage": "http://paypal.github.io/PayPal-PHP-SDK/",
-    "authors": [
-        {
-            "name": "PayPal",
-            "homepage": "https://github.com/paypal/rest-api-sdk-php/contributors"
-        }
-    ],
-    "require": {
-        "php": ">=5.3.0",
-        "ext-curl": "*",
-        "ext-json": "*",
-        "psr/log": "^1.0.0"
-    },
-    "require-dev": {
-        "phpunit/phpunit": "^4.8.35"
-    },
-    "autoload": {
-        "psr-0": {
-            "PayPal": "lib/"
-        }
-    }
-}
+{
+    "name": "simplesurance/paypal-rest-api-sdk-php",
+    "description": "PayPal's PHP SDK for REST APIs",
+    "keywords": ["paypal", "payments", "rest", "sdk"],
+    "type": "library",
+    "license": "Apache-2.0",
+    "homepage": "http://paypal.github.io/PayPal-PHP-SDK/",
+    "authors": [
+        {
+            "name": "PayPal",
+            "homepage": "https://github.com/paypal/rest-api-sdk-php/contributors"
+        }
+    ],
+    "require": {
+        "php": ">=8.1.0",
+        "ext-curl": "*",
+        "ext-json": "*",
+        "psr/log": "^1.0.0"
+    },
+    "require-dev": {
+        "phpunit/phpunit": "^4.8.35"
+    },
+    "autoload": {
+        "psr-0": {
+            "PayPal": "lib/"
+        }
+    }
+}
diff --git a/lib/PayPal/Common/ReflectionUtil.php b/lib/PayPal/Common/ReflectionUtil.php
index f7b397a..c661934 100644
--- a/lib/PayPal/Common/ReflectionUtil.php
+++ b/lib/PayPal/Common/ReflectionUtil.php
@@ -127,17 +127,6 @@ public static function propertyAnnotations($class, $propertyName)
         return $annotations;
     }
 
-    /**
-     * preg_replace_callback callback function
-     *
-     * @param $match
-     * @return string
-     */
-    private static function replace_callback($match)
-    {
-        return ucwords($match[2]);
-    }
-
     /**
      * Returns the properly formatted getter function name based on class name and property
      * Formats the property name to a standard getter function
@@ -148,8 +137,12 @@ private static function replace_callback($match)
      */
     public static function getter($class, $propertyName)
     {
+        $callback = function (array $matches) {
+            return ucwords($matches[2]);
+        };
+
         return method_exists($class, "get" . ucfirst($propertyName)) ?
             "get" . ucfirst($propertyName) :
-            "get" . preg_replace_callback("/([_\-\s]?([a-z0-9]+))/", "self::replace_callback", $propertyName);
+            "get" . preg_replace_callback("/([_\-\s]?([a-z0-9]+))/", $callback, $propertyName);
     }
 }