diff --git a/php/tests/php_implementation_test.php b/php/tests/php_implementation_test.php
index 4f626f1..6b922a9 100644
--- a/php/tests/php_implementation_test.php
+++ b/php/tests/php_implementation_test.php
@@ -366,6 +366,36 @@
             $this->assertSame(32768, $var);
         }
         $this->assertFalse($input->readVarint64($var));
+
+        // Read 64 testing
+        if (PHP_INT_SIZE > 4) {
+            $testVals = array(
+                '10'                 => '0a000000000000000000',
+                '100'                => '64000000000000000000',
+                '800'                => 'a0060000000000000000',
+                '6400'               => '80320000000000000000',
+                '70400'              => '80a60400000000000000',
+                '774400'             => '80a22f00000000000000',
+                '9292800'            => '8098b704000000000000',
+                '74342400'           => '80c0b923000000000000',
+                '743424000'          => '8080bfe2020000000000',
+                '8177664000'         => '8080b5bb1e0000000000',
+                '65421312000'        => '8080a8dbf30100000000',
+                '785055744000'       => '8080e0c7ec1600000000',
+                '9420668928000'      => '808080dd969202000000',
+                '103627358208000'    => '808080fff9c717000000',
+                '1139900940288000'   => '808080f5bd9783020000',
+                '13678811283456000'  => '808080fce699a6180000',
+                '109430490267648000' => '808080e0b7ceb1c20100',
+                '984874412408832000' => '808080e0f5c1bed50d00',
+            );
+
+            foreach ($testVals as $original => $encoded) {
+                $input = new InputStream(hex2bin($encoded));
+                $this->assertTrue($input->readVarint64($var));
+                $this->assertSame($original, $var);
+            }
+        }
     }
 
     public function testReadVarint32()