add non-string check parameter in __construct

src/Escaper.php

@@ -95,7 +95,11 @@ class Escaper
     public function __construct($encoding = null)
     {
         if ($encoding !== null) {
-            $encoding = (string) $encoding;
+            if (! is_string($encoding)) {
+                throw new Exception\InvalidArgumentException(
+                    get_class($this) . ' constructor parameter must be a string, received ' . gettype($encoding)
+                );
+            }
             if ($encoding === '') {
                 throw new Exception\InvalidArgumentException(
                     get_class($this) . ' constructor parameter does not allow a blank value'

test/EscaperTest.php

@@ -175,6 +175,15 @@ public function setUp()
         $this->escaper = new Escaper('UTF-8');
     }
 
+    /**
+     * @expectedException \Zend\Escaper\Exception\InvalidArgumentException
+     * @expectedExceptionMessage Zend\Escaper\Escaper constructor parameter must be a string, received integer
+     */
+    public function testSettingEncodingToNonStringShouldThrowException()
+    {
+        $escaper = new Escaper(1);
+    }
+
     /**
      * @expectedException \Zend\Escaper\Exception\InvalidArgumentException
      */