title: PHP reload issue
body: <p>I have the following php script:</p>
  
  <pre><code>&lt;?php
  
  $name = $_REQUEST['name'];
  $email = $_REQUEST['email'];
  $subject = $_REQUEST['subject'];
  $message = $_REQUEST['message'];
  $submit = $_REQUEST['submit'];
  $to = "torayevagajan@gmail.com";
  
  if(isset($submit))
  {
  
      function isValidEmail($email)
      {
          return eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email);
      }
  
      if(!empty($name) &amp;&amp; !empty($email) &amp;&amp; !empty($message) &amp;&amp; isValidEmail($email))
      {
          $text = "From: ".$email."&lt;br&gt;Name: ".$name."&lt;br&gt;".$message;
          if(mail($to, $subject, $text) &amp;&amp; !empty($submit)){
              echo "&lt;script type=\"text/javascript\"&gt;alert(\"Your message has been sent!\");&lt;/script&gt;";
              }
          else{
              echo "&lt;script type=\"text/javascript\"&gt;alert(\"Error Occured!\");&lt;/script&gt;";
              }
      }elseif(empty($name) || empty($email) || empty($message))
      {
          echo "&lt;script type=\"text/javascript\"&gt;alert(\"Please fill in the all fields!\");&lt;/script&gt;";
      }else echo "&lt;script type=\"text/javascript\"&gt;alert(\"Incorrect email format!\");&lt;/script&gt;";
  
      unset($submit);
  }
  ?&gt;
  </code></pre>
  
  <p>I have the following problem, after submitting details to contact php, whenever I want to refresh page, it tries again and again send mail, I mean it tries to run script, even I unset($submit); how can fix this?</p>