php - Parse error unexpected ":" Works fine in localhost

I have a PHP application with me, which was done by myself and a few of us. I have not coded much, but it worked well in the localhost. When I tried to upload it in our university web server, I had got this error.

Parse error unexpected :

This happened on this line. So I believe that PHP has to do something with respect to the previous line too. So I am adding the previous and next lines:

  session_start();
  $page = $_GET["page"] ?: "index"; // Error in this line!

The funny part is, this works on my WAMP Server locally, but it doesn't work in the university server. Is there any issue with the code?

Answer

I believe the PHP in your University Web Server is very old or older than 5.3. This is a shorthand ternary operator and is supported by PHP versions 5.3 and above.

Workaround

$page = $_GET["page"] ? $_GET["page"] : "index";

Update: To remove the warning, where $_GET["page"] is not set, you can use:

$page = isset($_GET["page"]) ? $_GET["page"] : "index"; // Checks if $_GET["page"] exists, and then assigns it.

PHP 7 will allow to use this short syntax:

$page = $_GET["page"] ?? "index";

From the docs:

Since PHP 5.3, it is possible to leave out the middle part of the ternary operator. Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise.