What are Common Functions in Codeigniter?

CodeIgniter library functions and helper functions need to be initialized before they are used but there are some common functions, which do not need to be initialized.

These common functions and their descriptions are given below.

Syntax	is_php($version)
Parameters	$version (string) − Version number
Return	TRUE if the running PHP version is at least the one specified or FALSE if not
Return Type	void
Description	Determines if the PHP version being used is greater than the supplied version number.

Syntax	is_really_writable($file)
Parameters	$file (string) − File path
Return	TRUE if the path is writable, FALSE if not
Return Type	bool
Description	checks to see if file is writable or not.

Syntax	config_item($key)
Parameters	$key (string) − Config item key
Return	Configuration key value or NULL if not found
Return Type	mixed
Description	This function is used to get the configuration item

Syntax	set_status_header($code[, $text = ''])
Parameters	$code (int) − HTTP Response status code $text (string) − A custom message to set with the status code
Return
Return Type	void
Description	This function permits you to manually set a server status header.

Syntax	remove_invisible_characters($str[, $url_encoded = TRUE])
Parameters	$str (string) − Input string $url_encoded (bool) − Whether to remove URLencoded characters as well
Return	Sanitized string
Return Type	string
Description	This function prevents inserting NULL characters between ASCII characters

Syntax	html_escape($var)
Parameters	$var (mixed) − Variable to escape (string or array)
Return	HTML escaped string(s)
Return Type	mixed
Description	This function acts as a native PHP htmlspecialchars() function.

Syntax	get_mimes()
Return	An associative array of file types
Return Type	array
Description	This function returns a reference to the MIMEs array from application/config/mimes.php.

Syntax	is_https()
Return	TRUE if currently using HTTP-over-SSL, FALSE if not
Return Type	bool
Description	Returns TRUE if a secure (HTTPS) connection is used and FALSE in any other case (including non-HTTP requests).

Syntax	is_cli()
Return	TRUE if currently running under CLI, FALSE otherwise
Return Type	bool
Description	Returns TRUE if the application is run through the command line and FALSE if not.

Syntax	function_usable($function_name)
Parameters	$function_name (string) − Function name
Return Type	bool
Description	Returns TRUE if a function exists and is usable, FALSE otherwise.

Given below is an example, which demonstrates all of the above functions.

Example

Here we have created only one controller in which we will use the above functions. Copy the below given code and save it atapplication/controller/CommonFun_Controller.php.

<?php 
   class CommonFun_Controller extends CI_Controller { 
 
      public function index() {
         set_status_header(200); 
         echo is_php('5.3')."<br>"; 
         var_dump(is_really_writable('./Form.php')); 
   
         echo config_item('language')."<br>"; 
         echo remove_invisible_characters('This is a ‌test','UTF8')."<br>"; 
   
         $str = '< This > is \' a " test & string'; 
         echo html_escape($str)."<br>"; 
         echo "is_https():".var_dump(is_https())."<br>"; 
         echo "is_cli():".var_dump(is_cli())."<br>"; 
   
         var_dump(function_usable('test'))."<br>"; 
         echo "get_mimes():".print_r(get_mimes())."<br>"; 
      } 
  
      public function test() { 
         echo "Test function"; 
      } 
  
   } 
?>

Change the routes.php file at application/config/routes.php to add route for the above controller and add the following line at the end of the file.

$route['commonfunctions'] = 'CommonFun_Controller';

Type the following URL in the address bar of your browser to execute the example.

http://yoursite.com/index.php/commonfunctions