title: Checking if e-mail address is already used
body: <p>I'm coding a registration system on php. I'm trying to make it impossible to create two accounts with same e-mail address. I wrote a code which should check it, but it doesn't work. I can create as many accounts as I want with the same e-mail. What's wrong with it?</p>
  
  <pre><code>$sqlemail = "SELECT count(*) FROM 'users' WHERE email = ?"; 
  $result = $connection-&gt;prepare($sqlemail); 
  $result-&gt;execute($email); 
  $emailused = $result-&gt;fetch();
  
  if ($emailused!=false) {
      echo 'An account with this e-mail address already exists!';
  }
  </code></pre>