title: PHP: Why does my strip_tags('<', '<br>') return empty string?
body: <p>I have a function that is used to strip unwanted HTML tag.
  e.g </p>
  
  <pre><code>function getValidStrings($inputStr, $allowedTag) {
     return trim(strip_tags($inputStr, $allowedTag));
  } // End function
  
  // Here I am calling this function which is defined in an included php Class file
  $formatter = new $StringTextFormatter;
  
  $validString = $formatter-&gt;getValidStrings('&lt;', '&lt;br&gt;');
  // The $validString has empty string "" ... Why ?
  </code></pre>
  
  <p>When I pass '&lt;' character to strip_tags, it returns empty. 
  However, strip_tags does give correct char if I pass in '>'. </p>
  
  <p><strong>I need to be able to return '&lt;' from above call. 
  Any idea what the solution could be?</strong></p>