PHP - 50％的时间输出2个不同的链接

I am doing a php lab and one of my tasks is to: do a “rick-roll” for a link. You are to output a link ( tag) that contains cat image ( tag). 50% of the time, your code will have the link go to the correct video, the other 50% of the time the link will go to a video of Rick Ashley’s song “Never Going to Give You Up” This task will require an if-else statement.

I know that using an if/else statement using the mt_rand(0,1) function will give me a 50% chance since it will either be 1 or 0 but I don't know how to make the links go to the correct video or Rick Astley's song. Here is my code:

<!-- TASK 2 -- Write your PHP code in in the space provided below.   -->
      <div class="task">
          <h2> Task 2: Rick Roll </h2>
          <p> Click for a funny cat video! </p>
        <? php
            if (mt_rand(0,1) == 0) {
        header('https://www.youtube.com/watch?v=hY7m5jjJ9mM');
        exit;
    } else {
        header('https://www.youtube.com/watch?v=dQw4w9WgXcQ');
        exit;
    }

          <a href="https://www.youtube.com/watch?v=hY7m5jjJ9mM">
    <img src="https://images.pexels.com/photos/104827/cat-pet-animal-domestic-104827.jpeg?h=350&auto=compress&cs=tinysrgb" alt="cute cat" width="250" height="250":>
    </a>
          <!--?php

            /* Task 2: Put your code here */


           ?-->

      </div>

You can save the link in a PHP variable

if (<your logic here>) {
 $link = "http://link1.com";
}
else {
 $link = "http://link2.com";
}

and using it in HTML <a> tag like this

<a href='<?php echo $link; ?>'>Link Name</a>