title: How consistent is FILTER_VALIDATE_EMAIL?
body: <p>Sample valid e-mail address:</p>
  
  <blockquote>
    <p>"this is a valid address"@example.com</p>
  </blockquote>
  
  <p>PHP code:</p>
  
  <pre><code>&lt;?php
  header('Content-Type: text/plain');
  
  $email = '"this is a valid address"@example.com';
  $checked = filter_var($email, FILTER_VALIDATE_EMAIL);
  var_dump($email, $checked);
  </code></pre>
  
  <p>Output on one server: (PHP Version 5.2.6):</p>
  
  <blockquote>
    <p>string(37) ""this is a valid address"@example.com"<br>
    string(37) ""this is a valid address"@example.com"</p>
  </blockquote>
  
  <p><code>phpinfo()</code>:</p>
  
  <pre class="lang-none prettyprint-override"><code>Input Validation and Filtering      enabled
  Revision                            $Revision: 1.52.2.42 $
  
  Directive             Local Value   Master Value
  filter.default        unsafe_raw    unsafe_raw
  filter.default_flags  no value      no value
  </code></pre>
  
  <p>Output on another server (PHP Version 5.3.3):</p>
  
  <blockquote>
    <p>string(37) ""this is a valid address"@example.com"<br>
    bool(false)</p>
  </blockquote>
  
  <p><code>phpinfo()</code>:</p>
  
  <pre class="lang-none prettyprint-override"><code>Input Validation and Filtering      enabled
  Revision                            $Revision: 298196 $
  
  Directive             Local Value   Master Value
  filter.default        unsafe_raw    unsafe_raw
  filter.default_flags  no value      no value
  </code></pre>
  
  <p>I cannot see anything in <a href="http://php.net/manual/en/filter.filters.validate.php" rel="nofollow noreferrer">the documentation</a> to suggest that this has changed, so perhaps it's some other configuration setting.</p>