first of all we need to create a simple xhtml form, like so:
HTML
<form method="post" action="<?=$PHP_SELF?>">
 Page name: <input name="page_name" size="27" />
 <select name="page_extension">
  <option value=".php">.php</option>
 </select>
 <br /><input type="submit" name="add_new_page" value="Add Page" />
</form

<?php
if($_POST['add_new_page']){//If the form has been submit
   
           $page_name = strip_tags($_POST['page_name']);//Post the page name, remove all html from it
        
        $page_extention = strip_tags($_POST['page_extension']);//Post the page extension, remove all html from it
        
        $filename = "files/".$page_name."".$page_extension."";//The location to send the new file
        
        $handle = fopen($filename, "x")or die("<strong>Cannot create file!</strong><br />");//Create the new file
        
        chmod("$filename","0777");//CHMOD the file to 0777 so it can be edited using the system!
        
        if (fwrite($handle, "Content goes here") === FALSE) {//If it cant write to the file
        
             print "Cannot write to file (".$filename.")";//Error msg
             exit;//Exit the script
          }
        
        print "Created file ".$page_name.", it is located ".$filename."<br />";//Success message
    
        fclose($handle);//Close the handle!
    
        print "Please wait 3 seconds to be redirected!<meta http-equiv=\"refresh\" content=\"3\">";//Done!
        
   }//End if
?>