PHP Basic -> Constant

Constant: constant means which is not going to change. Mainly we use constant  to declare a variable which is not going to change. for example to see the config file path.

You can define a constant by using the define()-function or by using the const keyword outside a class definition as of PHP 5.3.0.

Following are the way to set and get the constant value.

/** set the constant**/
define('CONFIG_FILE_PATH','/config');
/** set the constant**/

/** get the constant**/
echo CONFIG_FILE_PATH;
/** get the constant**/

Above CONFIG_FILE_PATH is constant, it is available in throughout the page. but it cannot be re-declare.



Following things keep in mind regarding this topic(Minimum)

• PHP constants Array
• PHP constants Class
• Use of define, constant etc
• How to check a variable defined or not
• How to check a constant is exist of not