HTML ignoring php tags and print plain text issue -

hi in html document i'm including some inside 1 of divs, prints php code plain text , kind of ignores php tags. here how code it.

    </form>        //just html tags right before php tags     <br/>     <br/>     <p id="hint"></p>  <?php                 // begining of php tags form(); function form(){     print "<form method='post' action='$_server[php_self]'>";     print"<input type='text' name='species'/>";      print"<input type='submit' name='submit'/>";      print"</form>";  }  echo '<div id='language_information'>'; ?>    </div>   <div style ="display:none;"id="about" title="how works">' 

here inspect element in chrome gives me, commented , plain text

  <p id="hint"></p>       <!--?php form(); function form(){     print "<form method='post' action='$_server[php_self]'-->        ";     print"     <input type="text" name="species"></input>       ";      print"     <input type="submit" name="submit"></input> 

make sure document extension should .php not .html.

in servers files .php extensions parsed, if use php in html file extension should .php