title: generate a unique id for every hit at one time
body: <p>Suppose many users uploading their pics at one time. So how could i generate a unique id for every pic which could never match with other generated id.</p>
  
  <pre><code>$uniqId = time().'_'.rand();
  </code></pre>
  
  <p>or should is use.</p>
  
  <pre><code>uniqid();
  </code></pre>