This is more correct according to the spec.

progrium · progrium · commit 082a66b1f233 · 2011-06-29T14:16:06.000-07:00
diff --git a/JWT.php b/JWT.php
@@ -53,7 +53,7 @@ public static function decode($jwt, $key = null, $verify = true)
      */
     public static function encode($payload, $key, $algo = 'HS256')
     {
-        $header = array('typ' => 'jwt', 'alg' => $algo);
+        $header = array('typ' => 'JWT', 'alg' => $algo);
 
         $segments = array();
         $segments[] = JWT::urlsafeB64Encode(JWT::jsonEncode($header));

Original file line number	Diff line number	Diff line change
`@@ -53,7 +53,7 @@ public static function decode($jwt, $key = null, $verify = true)`
`53`	`53`	`*/`
`54`	`54`	`public static function encode($payload, $key, $algo = 'HS256')`
`55`	`55`	`{`
`56`		`- $header = array('typ' => 'jwt', 'alg' => $algo);`
	`56`	`+ $header = array('typ' => 'JWT', 'alg' => $algo);`
`57`	`57`
`58`	`58`	`$segments = array();`
`59`	`59`	`$segments[] = JWT::urlsafeB64Encode(JWT::jsonEncode($header));`