Syntax explaination

Question

Hi, I am new at php.
I need to understand what does the colon before user_id(":user_id") mean in the second line.
<code>
$stmt = $auth_user->runQuery("SELECT * FROM users WHERE user_id=:user_id");
$stmt->execute(array(":user_id"=>$user_id));
$userRow=$stmt->fetch(PDO::FETCH_ASSOC);
</code>
Thanks for your time.

Answer 1

Before "user_id" I think it's not semicolon, it's a colon.😊

Answer 2

You are right . I have corrected it.Can you please explain that line?