title: PHP Make a simple if-isset-empty function
body: <p>I'm coding a worksheet app for a printer company. 
  I'm getting flood of forms. 
  For every single input field I have to check if the <code>$_POST</code> variables are set, and if, so echo back the value. (In case of some error, for example after a validation error, the user shouldn't retype the whole form)</p>
  
  <p>Sample code:</p>
  
  <pre><code>if(isset($_POST['time'])&amp;&amp;!empty($_POST['time'])){echo $_POST['time'];}
  </code></pre>
  
  <p>I had to implement this about a hundred times. 
  So I tried to figure out some kind of function to make this simple and readable.</p>
  
  <p>Something like this:</p>
  
  <pre><code>function if_post_echo($key, $default = "") {
      if(isset($_POST[$key])&amp;&amp;!empty($_POST[$key])){
      echo $_POST[$key];   
      }else{
      echo $default;   
      }
  }
  </code></pre>
  
  <p>But this wont work.
  I have tried to pass in the <code>$_POST</code> for the <code>$key</code> variable like this:</p>
  
  <pre><code>if_post_echo($_POST['time'])
  
  function if_request_echo($key, $default = "") {
          if(isset($key)&amp;&amp;!empty($key)){
          echo $key;   
          }else{
          echo $default;   
          }
      }
  </code></pre>
  
  <p>And I also tried this:</p>
  
  <pre><code>function if_request_echo($key, $default = null) {
      return isset($_REQUEST[$key])&amp;&amp;!empty($_REQUEST[$key]) ? $_REQUEST[$key] : $default;
  }
  </code></pre>
  
  <p>Without any reasonable outcome.</p>
  
  <h3>The question:</h3>
  
  <p>How can I forge a function that looks for the necessary <code>$_POST</code> variable and returns it or if its unset then returns an empty string. 
  And is there a way to do this for <code>$_GET</code> and <code>$_REQUEST</code>, too? (Or simply duplicate?)</p>