title: Issue with validate email using PHP
body: <p>I have the following code to check if user input is a valid email, there might be a few questions already about this but noone seems to validate the PHP function.</p>
  
  <pre><code>/* check if valid email*/
  public function isValidEmail($email){
      if(filter_var($email, FILTER_VALIDATE_EMAIL)) {
          return true;
      }
      return false;
  }
  </code></pre>
  
  <p>If we do a test using this function:</p>
  
  <pre><code>isValidEmail('some?=Wrong@mail.com') 
  </code></pre>
  
  <p>This should return <code>false</code> because characters like <code>?=</code> are inside the email address. Is there a stricter way to check email?</p>