title: Add data to $_POST and submit to another page
body: <p>I'm trying to add a value to $_POST data while it gets submitted to the target page as follows:</p>
  
  <p>post.php</p>
  
  <pre><code>&lt;?php  $_POST['field1'] = "Value1";?&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form method="post" action="catch.php"&gt;
          &lt;input name="field2" type="text"/&gt;
          &lt;input type="submit" value="Submit" /&gt;
      &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>catch.php</p>
  
  <pre><code>&lt;?php 
  foreach ($_POST as $key =&gt; $value) {
      echo $key . " : ". $value;
      echo "&lt;br/&gt;";
  }
  ?&gt;
  </code></pre>
  
  <p>but I cannot catch 'field1' on the other end. I don't want to use a hidden input field. How can I achieve that?
  Thanks!</p>