diff --git a/src/ArrayEnum.php b/src/ArrayEnum.php
index 0ac1b72..e790678 100644
--- a/src/ArrayEnum.php
+++ b/src/ArrayEnum.php
@@ -17,7 +17,7 @@ abstract class ArrayEnum extends Enum
      *
      * @var integer
      */
-    protected const LENGTH = 2;
+    protected static $ENUM_LENGTH = 2;
 
     /**
      * The enum key.
@@ -69,6 +69,28 @@ public function getValue()
         return $this->value;
     }
 
+    /**
+     * Compare the keys to be equal.
+     *
+     * @param mixed $key
+     * @return bool
+     */
+    public function keyEquals($key)
+    {
+        return $this->getKey() == $key;
+    }
+
+    /**
+     * Compare the values to be equal.
+     *
+     * @param mixed $value
+     * @return bool
+     */
+    public function valueEquals($value)
+    {
+        return $this->getValue() == $value;
+    }
+
     /**
      * Get the array enum all keys.
      *
@@ -100,9 +122,6 @@ public static function getValues($prefix = '')
         $constants = $reflectionClass->getConstants();
 
         foreach ($constants as $key => $value) {
-            if($key == 'LENGTH') {
-                continue;
-            }
             if(empty($prefix) || strstr($key, strtoupper($prefix))) {
                 $values[reset($value)] = end($value);
             }
@@ -112,6 +131,48 @@ public static function getValues($prefix = '')
 
     }
 
+    /**
+     * Determine if the key exists.
+     *
+     * @param mixed $key
+     * @param string $prefix
+     * @return bool
+     */
+    public static function keyExist($key, $prefix = '')
+    {
+
+        $values = self::getValues($prefix);
+
+        if(empty($values[$key])) {
+            return false;
+        }
+
+        return true;
+
+    }
+
+    /**
+     * Determine if the value exists.
+     *
+     * @param mixed $value
+     * @param string $prefix
+     * @return bool
+     */
+    public static function valueExist($value, $prefix = '')
+    {
+
+        $values = self::getValues($prefix);
+
+        $key = array_search($value, $values);
+
+        if(false === $key) {
+            return false;
+        }
+
+        return true;
+
+    }
+
     /**
      * Search the key based on the value.
      *
@@ -154,4 +215,19 @@ public static function searchValue($key, $prefix = '')
 
     }
 
+    /**
+     * Get enum size.
+     *
+     * @param string $prefix
+     * @return int
+     */
+    public static function getSize($prefix = '')
+    {
+
+        $values = self::getValues($prefix);
+
+        return count($values);
+
+    }
+
 }
diff --git a/src/Enum.php b/src/Enum.php
index f8f76b3..ca48cd3 100755
--- a/src/Enum.php
+++ b/src/Enum.php
@@ -17,7 +17,7 @@ abstract class Enum
      *
      * @var integer
      */
-    protected const LENGTH = 0;
+    protected static $ENUM_LENGTH = 0;
 
     /**
      * Create a new enum instance.
@@ -33,7 +33,7 @@ public function __construct($attributes)
         if(!is_array($attributes)) {
             throw new \InvalidArgumentException('Enum attribute only accepts array.');
         }
-        if($this->getLength() <= self::LENGTH) {
+        if($this->getLength() <= self::$ENUM_LENGTH) {
             throw new \LengthException('Enum attribute length must be greater than zero');
         }
         if($this->getLength() != count($attributes)) {
@@ -60,7 +60,7 @@ public static function __callStatic($name, $arguments)
      */
     public function getLength()
     {
-        return static::LENGTH;
+        return static::$ENUM_LENGTH;
     }
 
 }
diff --git a/src/ListEnum.php b/src/ListEnum.php
index afd602f..d1d2268 100644
--- a/src/ListEnum.php
+++ b/src/ListEnum.php
@@ -44,7 +44,7 @@ abstract class ListEnum extends Enum
      *
      * @var integer
      */
-    protected const LENGTH = 1;
+    protected static $ENUM_LENGTH = 1;
 
     /**
      * The attribute key index.