PHP Robot Check

I've seen quite a few methods for determining if a request was made by a robot or search engine spider using PHP over the years, and they always have something to do with checking the User Agent. That works, but you have to keep up with User Agent strings which can get to be annoying.

I had an idea how to check for robots using PHP and htaccess today that doesn't involve a User Agent string at all. Instead it uses sessions and exploits the fact that all well behaved robots are going to request robots.txt before they request anything else.

I start by making sure my usual robots.txt file is in place. Then I upload a robots.php file to the same location as robots.txt with a tiny bit of code in it.

<?php
session_start();
$_SESSION['robot'] = 1;
echo file_get_contents('robots.txt');
exit;
?>

All that does is start a session, set a robot $_SESSION variable that I can check in subsequent scripts, then return the contents of robots.txt.

In htaccess I have the following line which transparently redirects requests to robots.txt made by visitors/spiders to robots.php, which in turn returns the contents of robots.txt

RewriteEngine on
RewriteRule robots\.txt robots.php

Now in my applications I can easily check for robots and drop things like advertisement banners to speed up page loads since spiders don't look at advertisements anyway.

<?php
session_start();
echo isset($_SESSION['robot']) ? 'ROBOT !!' : 'Not a robot';
?>

Here are some of the benefits of doing it this way.

1. I can continue to modify robots.txt as I normally would
2. I don't need to keep up with changing User Agent strings
3. Checking for the existance of a session variable is quicker than performing pattern matching on a variable

Random Color Generation With Javascript

I'm sure there's quite a few ways to get a random color using JS, I can think of a few such as returning a random index from an array of CSS color names, or generating three random numbers between zero and 255 and formatting from there.

The following method is my favorite though because the single randomly generated integer can be easily converted into pretty much any other format or quickly returned as-is.
To illustrate this I've written the following function which will return a hexidecimal, RGB, or integer format random color depending on the argument passed to the function.

// @format (hex|rgb|null) : Format to return, default is integer
function random_color(format)
{
 var rint = Math.round(0xffffff * Math.random());
 switch(format)
 {
  case 'hex':
   return ('#0' + rint.toString(16)).replace(/^#0([0-9a-f]{6})$/i, '#$1');
  break;
  
  case 'rgb':
   return 'rgb(' + (rint >> 16) + ',' + (rint >> 8 & 255) + ',' + (rint & 255) + ')';
  break;
  
  default:
   return rint;
  break;
 }
}

50 Random PHP5 Facts

Here's a list of 50 49 random facts about PHP.

1. You MUST load PDO before loading any PDO drivers
2. An iterator cannot be used with foreach by reference
3. Cannot create references to elements of a temporary array expression
4. Cannot create references to/from string offsets nor overloaded objects
5. Cannot assign by reference to overloaded objects
6. Only variable references should be returned by reference
7. Only variables can be passed by reference
8. Cannot return string offsets by reference
9. Cannot use string offset as an array
10. Cannot use object as array -- See Dans comment
11. Cannot use a NULL value as an array
12. Cannot use a scalar value as an array
13. foreach() can not iterate over objects without PHP class
14. Cannot use assign-op operators with overloaded objects nor string offsets
15. __HALT_COMPILER() can only be used from the outermost scope
16. Assigning the return value of new by reference is deprecated
17. Variables passed to each() must be an array or object
18. Constants may only evaluate to scalar values
19. is_a() is deprecated. The "instanceof" operator should be used instead This has changed as of PHP 5.3, see Gregs comment
20. Cannot add internal functions to return value from get_defined_functions()
21. Cannot add user functions to return value from get_defined_functions()
22. Static functions cannot be abstract
23. Exceptions must be derived from the Exception base class
24. Need to supply an object when throwing an exception
25. Cannot declare self-referencing constants
26. Cannot use call_user_function on objects without a class entry
27. Cannot access self:: when no class scope is active
28. Cannot access parent:: when no class scope is active
29. Cannot access parent:: when current class scope has no parent
30. add_assoc_function() is no longer supported
31. Usage of {} to access string offsets is deprecated and will be removed in PHP 6
32. Cannot re-assign $this
33. __toString() must not throw an exception
34. Can't use method return value in write context
35. Can't use function return value in write context
36. Multiple access type modifiers are not allowed
37. Cannot use the final modifier on an abstract class member
38. Default value for parameters with a class type hint can only be NULL
39. Default value for parameters with array type hint can only be an array or NULL
40. Cannot call __clone() method on objects - 'clone $obj' should be used instead
41. Clone method does not require arguments
42. Interfaces cannot not implement themselves
43. Classes may not inherit from classes declared final
44. Classes cannot inherit previously-inherited constants from interfaces
45. Classes cannot implement previously-implemented interfaces
46. Class declarations may not be nested
47. Cannot use reserved words as class or interface names
48. Interfaces may not include member variables
49. Properties cannot be declared abstract
50. Cannot declare properties final, the final modifier is allowed only for methods

Silky Directory Indexes

I really like the Silk Icons at famfamfam, alot more than the default FancyIndex icons used by Apache2 in fact.
So, now seems like a good time to patch those icons into my directory indexes for FancyIndexing.

First I get the zipfile fill of icons, which is actually a zipfile that has two readme files & a directory called icons in it.

Next I navigate to the directory Apache is already using for icons

Alias /icons/ "/usr/share/apache2/icons/"

In my case it's /usr/share/... look for "Alias /icons" in your *.conf file for Apache to find out where it is for you.

Now, I extract the icons folder from the zipfile into Apaches' icons directory & rename the extracted directory to "silk" so that I have the following.

/usr/share/apache2/icons/silk/

Now to change the icons in the Virtual Host container for the site in question, *.htaccess files could also be used to use different icons per-directory.
I'll start with the ones that have listings already, making the following changes to the AddIcon lines.

    AddIconByEncoding (CMP,/icons/silk/page_white_zip.png) x-compress x-gzip

    AddIconByType (TXT,/icons/silk/page_white_text.png) text/*
    AddIconByType (IMG,/icons/silk/picture.png) image/*
    AddIconByType (SND,/icons/silk/sound.png) audio/*
    AddIconByType (VID,/icons/silk/film.png) video/*

    AddIcon /icons/silk/application_double.png .exe
    AddIcon /icons/silk/application_xp_terminal.png .bin
    AddIcon /icons/silk/page_white_zip.png .Z .z .tgz .gz .zip
    AddIcon /icons/silk/page_white_code.png .shtml
    AddIcon /icons/silk/page_white_acrobat.png .pdf
    AddIcon /icons/silk/page_white_zip.png .txt
    AddIcon /icons/silk/page_white_c.png .c
    AddIcon /icons/silk/page_white_cplusplus.png .cpp
    AddIcon /icons/silk/page_white_dvd.png .dvi
    AddIcon /icons/silk/page_white_gear.png .ini .conf .sh .shar .csh .ksh .tcl
    AddIcon /icons/silk/page_white_actionscript.png .as
    AddIcon /icons/silk/page_white_flash.png .fla .swf
    AddIcon /icons/silk/page_white_freehand.png .fh3 .fh4 .fh5 .fh7 .ft7 .fh8 .ft8 .fh9 .ft9 .fh10 .ft10 .fhx
    AddIcon /icons/silk/page_white_h.png .h
    AddIcon /icons/silk/page_white_php.png .php .php3 .php4 .php5
    AddIcon /icons/silk/page_white_office.png .docx .docm .dotx .dotm
    AddIcon /icons/silk/page_white_powerpoint.png .pptx .pptm .potx .potm .ppam .ppsx .ppsm
    AddIcon /icons/silk/page_excel.png .xlsx .xlsm .xltx .xltm .xlsb .xlam
    AddIcon /icons/silk/page_white_ruby.png .rb
    AddIcon /icons/silk/page_white_word.png .doc
    AddIcon /icons/silk/css.png .css
    AddIcon /icons/silk/html.png .html .htm
    AddIcon /icons/silk/xhtml.png .xhtml
    AddIcon /icons/silk/script_code.png .js
    AddIcon /icons/silk/database_table.png .sql
    AddIcon /icons/silk/script_gear.png .inc .pl .py
    AddIcon /icons/silk/help.png .chm
    AddIcon /icons/silk/music.png .wav .mp3 .ogg

    AddIcon /icons/silk/folder_delete.png ..
    AddIcon /icons/silk/asterisk_yellow.png README
    AddIcon /icons/silk/folder_add.png ^^DIRECTORY^^
    AddIcon /icons/blank.gif ^^BLANKICON^^


    DefaultIcon /icons/silk/page_white.png

Followed by a restart of Apache for good measure.

sudo /etc/init.d/apache2 restart

I now have silky icons on my directory indexes, but apparently it's going to need a little tweeking to tell the difference between "text/text", "text/html", & "text/css" somewhere.