PHP Constants
PHP Constants
PHP constants are name or identifier that can't be changed during the execution of the script except for magic constants, which are not really constants. PHP constants can be defined by 2 ways.
- Using define( ) function
- Using const keyword
- Numbers with decimal points are classified as floating points.
- True or false values are classified as Boolean.
Constants are similar to the variable except once they defined, they can never be undefined or changed. They remain constant across the entire program. PHP constants follow the same PHP variable rules. For example, it can be started with a letter or underscore only. Conventionally, PHP constants should be defined in uppercase letters.
Create a PHP Constant
To create a constant, use the define() function.
Syntax
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
<?php
define("GREETING", "Welcome to W3Schools.com!");
echo GREETING;
?>
PHP Constant Arrays
In PHP7, you can create an Array constant using the define( ) function.
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:
<?php
define("cars", [
"Alfa Romeo",
"BMW",
"Toyota"
]);
echo cars[0];
?>
Constants are Global
Constants are automatically global and can be used across the entire script.
This example uses a constant inside a function, even if it is defined outside the function:
<?php
define("GREETING", "Welcome to W3Schools.com!");
function myTest() {
echo GREETING;
}
myTest();
?>
