code: public static function highlight($strString, $strPhrase, $strOpeningTag='<strong>', $strClosingTag='</strong>')
  	{
  		if ($strString == '' || $strPhrase == '')
  		{
  			return $strString;
  		}
  
  		return preg_replace('/(' . preg_quote($strPhrase, '/') . ')/i', $strOpeningTag . '\\1' . $strClosingTag, $strString);
  	}
docs: Highlight a phrase within a string
  
  @param string $strString     The string
  @param string $strPhrase     The phrase to highlight
  @param string $strOpeningTag The opening tag (defaults to <strong>)
  @param string $strClosingTag The closing tag (defaults to </strong>)
  
  @return string The highlighted string