title: How to show an alert box in PHP?
body: <p>I want to display an alert box showing a message with PHP.</p>
  
  <p>Here is my PHP code:</p>
  
  <pre><code>&lt;?php  
    header("Location:form.php");
  
    echo '&lt;script language="javascript"&gt;';
    echo 'alert(message successfully sent)';  //not showing an alert box.
    echo '&lt;/script&gt;';
    exit;
  ?&gt;
  </code></pre>
  
  <p>But it is not working.</p>