title: If no arguments are provided in the function, how do I test to see if it is left blank?
body: <pre><code>&lt;?php    
  /* Copyright Date
  --------------------------*/
  function copyright_date($creation_year) {
      $current_year = date('Y');
  
      if ($creation_year == $current_year || $creation_year == '') {
          echo $current_year;
      } 
      else {
          echo $creation_year . '-' . $current_year;
      }           
  }
  ?&gt;
  </code></pre>
  
  <p>If someone forgets to add the argument (the year the website was created), e.g.</p>
  
  <pre><code>&lt;?php copyright_date(); ?&gt;
  </code></pre>
  
  <p>instead of:</p>
  
  <pre><code>&lt;?php copyright_date(2009); ?&gt;
  </code></pre>
  
  <p><strong>how would I test to see if the argument was left blank?</strong> In my if statement, that's what $creation_year == '' is for, but since the argument isn't a string, it doesn't work.</p>