The CI main configuration files have the following major configurations:

$config['base_url'] = '';

The default is an empty string so that CI can calculate the base URL of our project root directory. We shall refer to the base URL in many places in our code, mostly to execute controllers. To get the base URL, we should call:

$base_url = base_url();
// defined in the URL
// helper mentioned before.

The base_url() function in the URL helper function returns the URI string to the CI project base. For example, if the CI project is developed on a domain named example.com under a public_html directory named mydev, and we have a controller named find, a method named stock, and a directory named myprod, we can call the find or stock method in both the myprod and mydev projects using base_url():

$url = base_url()."index.php/ find/stock";

In the mydev project, we will get:

$url = "http://example.com/mydev/index.php/find/stock"

In the myprod project, we will get:

$url = "http://example.com/myprod/index.php/find/stock"

Hence, in order to call a controller class named my_class, we use:

$URL = base_url()."index.php/my_class/mymethod";

This will define $u rl as http://example.com/ mydev/index.php/my_class.

To set the index page as a part of the URI path to CI controllers/methods, we use:

$config['index_page'] = 'index.php';

The index.php file is the CI root PHP service that handles all the URI requests. It is used as part of a path URI to a resource, such as http://mysite.com/fci/index.php/tables_managemen t/show. However, we can hide the index.php file by setting CI to hide the index.php file in the URI path for calling the CI resources such as http://mysite.com/fci/tables_managemen t/show. To do so, we need to perform the following configuration steps:

The .htaccess file does the trick here by adding the index.php file to the URI after receiving the URI request from the browser and before executing it. The result is that the user who is browsing will not see it, but it will call the desired resource properly, in a similar way to how we used index.php:

The language setting is done as follows:

$config['language'] = 'english';

It is recommended that you leave this as default. Note that even if we use other languages, such as Arabic or Hebrew, it will be fine. We just make sure that our PHP files are saved as UTF-8 without BOM (byte order mark is a unicode character that marks the file-encoding method supporting multilanguage schemes; for more information, refer to http://en.wikipedia.org/wiki/Byte_order_mark to inform the browser that receives the rendered HTML page to process it as a UTF-8 file.

The exact meaning of this tag is out of the scope of this book and can be learned from HTML standard.

$config['charset'] = 'UTF-8';

Additionally, it is highly recommended for multi-language support to add the following line in our view file's HTML header:

<meta http-equiv="Content-Type"
content="text/html; charset=utf-8" />

These settings inform the browser to process the rendered HTML page whose characters are encoded as UTF-8, which is the most common multilanguage standard for non-English languages such as Hebrew, Arabic, and Chinese.

Do not touch these settings; it is very useful to support multiple languages.

$config['enable_hooks'] = FALSE;

The preceding configuration, if set to TRUE, will enable us to define hooks into CI events, where the hooks are defined in the application/hooks directory. Do not touch these settings unless you have a specific plan for CI event hooks. Note that the concept of adding hooks to the CI core activity is out of this book's scope.

$config['subclass_prefix'] = 'MY_';

The preceding configuration will enable us to define naming roles to our library class name's prefix, in order to distinguish with other default libraries.

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-';

The preceding code defines the allowed chars within a URI calling CI resources, mainly controllers. It is recommended to not touch this setting.

$config['allow_get_array'] = TRUE;

This will enable us to call the controller class methods with parameters, such as in the example provided earlier.

<?php echo base_url(); ?>index.php/my_handler/calc/5/7

The preceding code will provide the same results as the class method within the my_handler class itself in the following format:

$Val= $this->calc(5,7);

The following configuration defines if a GET URL query string will be used:

$config['enable_query_strings'] = FALSE;

This configuration, if set to TRUE, will enable us to call controller class methods with parameters in the GET URL query form:

<?php echo base_url();?>index.php/my_handler/calc.php?a=5&b=7

It is highly recommended to leave this as FALSE, as CI provides a solution to pass parameters within URI, as shown in the calc example at the beginning of this chapter.

The log threshold for the severity level is such that any event that is of the same or higher severity level will be logged to CI. The supported threshold levels and their meanings are as follows:

The preceding configuration will generate error logs according to the log_threshold () level at /application/logs if the error log was enabled.

Note that enabling the errors log will cause performance reduction in our web application. Use it only if you must for debugging needs. Otherwise set it to 0.

$config['log_path'] = '';

The default log file path in the CI project is application/logs. Do not touch this configuration unless you have a clear reason.

The date time format:

$config['log_date_format'] = 'Y-m-d H:i:s';

The default date time format setting is 2012-06-18 14:54:11. It is recommended to not touch this configuration.

The cache file path:

$config['cache_path'] = '';

The default is application/cache. It is recommended not to touch this configuration. The session key:

$config['encryption_key'] = '';

This encryption_key must be set with a key in order to use the session class services. For example:

$config['encryption_key'] = 'cMGy4DSwGUvxYSar4279626HgOn2342efrwerr2TE2RF4G3reg4tF3etf';

An example of the session library usage within a controller and setting a session variable is as follows:

$uid = 119; // where uid is the id of the loggeing user
$this->session->set_userdata ('this_user_id', $uid );

Getting the session variable in another controller is as follows:

$uid = $this->session->userdata('this_user_id');

The session data storage mechanism is as follows:

$config['sess_use_database'] = FALSE;

If the recommended configuration is set to TRUE, we would use many session parameters of a large size stored in the associated default database.

Session expiration timeout in seconds:

$config['sess_expiration'] = 7200;
// The number of seconds the session will be kept

Additional session configuration parameters can be found in the CI user manual. Cross-site scripting (XSS) filtering activation/deactivation:

$config['global_xss_filtering'] = FALSE;

This will enable XSS filtering on URI requests sent to the application. Note that all URI requests are processed initially by the root index.php to analyze the URI request and issue the proper CI calls. If set to TRUE it will protect URI requests from XSS type malicious attackers. It is recommended to set it to TRUE even if we reduce a bit of our application performance.

$config['csrf_protection'] = FALSE;

If set to TRUE the CI will prevent Cross-Site Request Forger y (CSRF/XSRF) attacks. The risk is when the fraud form is submitted. If we are accepting user data, it is strongly recommended that CSRF protection should be enabled. Note that when using AJAX, additional code may be required to enable CSRF protection with AJAX.

The database configuration enables to define one or more database connections that can be used by the application. The database configuration is a two-dimensional array in the following form:

$db['db_entry']['db_connection_param']

By setting the parameters for database default entry, we shall define the following parameters:

$db['default']['hostname'] = 'localhost';
// note: in some cases '127.0.0.1' must be used instead 
// localhost if the database server is in another server use
// URI such as: 'domain.db.NNNNNNN.hostedresource.com' or 
// similar – advise our system admin/service provider
// Optional configuration of DB server connection port

$db['default']['port'] = '4009';
// In case our DB server operates on another port
// otherwise we may drop the port config line!

$db['default']['username'] = 'mydefaultdb';
$db['default']['password'] = 'mypass1';
$db['default']['database'] = 'mydatabase1';
$db['default']['dbdriver'] = "mysql";
$db['default']['dbprefix'] = "";
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = TRUE;
$db['default']['cachedir'] = "";
$db['default']['char_set'] = "utf8";
$db['default']['dbcollat'] = "utf8_general_ci";

By setting the parameters for another database entry named dbentry2, we shall define the following parameters:

$db['dbentry2']['hostname'] = 'localhost';
$db['dbentry2']['username'] = 'mySecondDB';
$db['dbentry2']['password'] = 'mypass2';
$db['dbentry2']['database'] = 'mySecondDB';
$db['dbentry2']['dbdriver'] = "mysql";
$db['dbentry2']['dbprefix'] = "";
$db['dbentry2']['pconnect'] = TRUE;
$db['dbentry2']['db_debug'] = TRUE;
$db['dbentry2']['cache_on'] = TRUE;
$db['dbentry2']['cachedir'] = "";
$db['dbentry2']['char_set'] = "utf8";
$db['dbentry2']['dbcollat'] = "utf8_general_ci";

There is no need to connect and load the default database as it is done automatically when loading the database class—however, the call is:

$this->load->database();

Or, for referring to a specific database entry name, it is:

$this->load->database('default');

In order to connect and load the dbentry2 database settings stated earlier, use the following code:

$this->dbentry2= $this->load->database(dbentry2', TRUE); 

To use the default database with the database class library, db, use:

$q1 = $this->db->query ("select * from mytable");

To use the dbentry2 database, use:

$q2 = $this->dbentry2->db->query ("select * from DB2table");

Define the default controller that will be executed when referred via the URI to the base_url of the project—let's say http://mydomain.com/myapp so that myapp is a subdirectory of public_html in the sever and we have home_page_controller.

$route['default_controller'] = "home_page_controller"

When the user issues http://mydomain.com/myapp, due to the route configuration for the home controller, the URI that CI will issue will be as if the user is referring to http://mydomain.com/myapp/home_page_controller.

$route['404_override'] = '';

In the preceding example, the default application/errors/error_404.php page will be executed, in case the user refers to a non-existing project controller, such as http://mydomain.com/myapp/sadfasdfsdfsdi.

We may decide, for example, to pop-up a message for the non-existing page and route to the default URI to minimize user inconvenience.