Power 2 Protect: Restrict user access to pages based on permissions

 Power 2 Protect PHP Class
 Author: Igor Feghali
 Email: ifeghali@interveritas.net

 [DESCRIPTION]
 This class verifies if a user have
 access to the current page by requesting a mysql
 database record and then take the user to a error
 page if the record doesn't match the user's key.

 [MySQL TABLE STRUCTURE REQUIRED OR EQUIVALENT]

 USERTYPE          PERMISSIONS
 ($table_usertype) ($table_perm)
 |---------------| |---------------|---------------|
 |usertype(int)  | |accesskey(int) |page(char)     |
 |---------------| |---------------|---------------|
 | 2^0           | | x             |/dir/page1.php |
 | 2^1           | | y             |/dir2/page2.php|
 | ...           | | z             |page3.php      |
 | 2^(n-1)       | | w             |/dir3/page4.php|
 |---------------| |---------------|---------------|

 USER
 ($table_user)
 |-------------|-----------|---------|-------------------|
 |usercode(int)|login(char)|pwd(char)|usertype(int)      |
 |-------------|-----------|---------|-------------------|
 | 1           | login1    | pwd1    | 2^a               |
 | 2           | login2    | pwd2    | 2^b               |
 |-------------|-----------|---------|-------------------|

 [[WHERE]]
 "n" is the number of records in USERTYPE.
 a,b is an integer and 2^a and 2^b must have a
 correspondent in USERTYPE.
 x,y,z,w is an integer [0,1,2,3,7,...,2^(n-1)] and
 is obtained by the sum of the usertypes you want
 to grant access.

 Note: you must provide the whole path after
 your domain's root dir.
 Example: for a script located at
 www.yourdomain.com/dir1/script.php you should
 fill "page" with "/dir1/script.php".

 [INSTALL]
 Edit file config.inc.php.
 Create the tables USERTYPE, PERMISSIONS and USER
 (or the names you set on the variables) following 
 the model under the MySQL table structure topic of
 this document. If you want to use the default table
 names, you can run the script create_tables.sql
 to automatically create them. Make sure you gave 
 MYSQLUSER access to MYSQLDB.

 [SETUP PROTECTION]
 Add user types to USERTYPE using powers of 2.
 Add to PERMISSIONS the relative path to the
 file you want to protect associated to an accesskey 
 obtained by the sum of the usertypes you wish to 
 grant access. Include the file protect.php in the
 script you have just added to PERMISSIONS.

 [EXAMPLES]
 For table examples you can check file create_tables.sql.
 For an example on how to protect a page you can check
 the file admin.php.