title: Ignore case sensitivity when comparing strings in PHP
body: <p>I'm trying to compare words for equality, and the case [upper and lower] is irrelevant.
  However PHP does not seem to agree! Any ideas as to how to force PHP to ignore the case of words while comparing them?</p>
  <pre><code>$arr_query_words = [&quot;hat&quot;,&quot;Cat&quot;,&quot;sAt&quot;,&quot;maT&quot;];
  for( $j= 0; $j &lt; count($arr_query_words); $j++ ){
      $story_body = str_replace( 
          $arr_query_words[ $j ],
          '&lt;span style=&quot; background-color:yellow; &quot;&gt;' . $arr_query_words[ $j ] . '&lt;/span&gt;',
          $story_body
     );
  }
  </code></pre>
  <p>Is there a way to carry out the replace even if the case is different?</p>