A constant is a value cannot change during the execution of the program. By default, it is case-sensitive. A constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.
If you have defined a constant, it can never be changed or undefined.
To define a constant you have to use define() function and to retrieve the value of a constant, you have to simply specifying its name.You can also use the function constant() to read a constant's value if you wish to obtain the constant's name dynamically.
Constants are automatically global and can be used across the entire script.
To create a constant, use the define() function.
define(name, value, case-insensitive)
- name: Specifies the name of the constant.
- value: Specifies the value of the constant.
- case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false.
<!DOCTYPE html> <html> <body> <?php case-insensitive constant name define("GREET", "Welcome to tutu’rself!", true); echo greet; ?> </body> </html>
Welcome to tutu’rself!