title: How to check when request was send
body: <p>I'm running several requests (A, B, C, ...) and they are queued to happen sequentially: B waits for A to complete, C waits for B, and so on. I want to get the timestamp of the moment when they <em>get into the queue</em>. I can get the timestamp of the request when it's <em>actually happening</em>, that is, the time of B when A is already done - <code>$_SERVER['REQUEST_TIME']</code> gives me that, but that's not what I want. I'd like to have the precise times of getting into the queue, no matter when they arrive to the server.</p>
  
  <p>Sending timestamp as an additional GET parameter doesn't seem safe enough because it can be forged on client side. Is there another way?</p>