The element mask is 0 rather than false if element not fount.

Author: mattfarina

src/HTML5/Elements.php

@@ -557,7 +557,7 @@ public static function isElement($name)
      * @param string $name
      *            The name of the element.
      *
-     * @return int|bool The element mask or false if element does not exist.
+     * @return int The element mask.
      */
     public static function element($name)
     {
@@ -571,7 +571,7 @@ public static function element($name)
             return static::$mathml[$name];
         }
 
-        return false;
+        return 0;
     }
 
     /**

test/HTML5/ElementsTest.php

@@ -351,7 +351,7 @@ public function testElement()
             'baz'
         );
         foreach ($nonhtml5 as $element) {
-            $this->assertFalse(Elements::element($element));
+            $this->assertEquals(0, Elements::element($element));
         }
     }