PHP is a server-side scripting language used to develop static and dynamic websites or certain web applications.
A constant is an identifier that cannot be changed during the course of the script. Changing the value stored inside a constant will result in an error. There are many types of constants in a computer; one commonly used value is pi. Whatever the course of a program, the value of pi is one such example that cannot be changed at any point in the script.
Generally, constants are global across the entire script.
Variables in PHP are defined using the $ sign:
$x = 5;
$str = "Hello World";
However, to define a constant, we will use the define() function.
Syntax:
define(name, value)
/*
Parameters: name: Specifies the name/identifier of the constant.
e.g pi, a, b, c.
value: Specifies the value to be stored in the constant.
*/
<?php// define a constant a with value 2;define(a,2);echo a; // print aecho "\n";// define a constant string hdefine("h","New string");echo h; // print hecho "\n";//define a constant boolean value x;define(x,true);echo x; //print x// the output of the code will show a warning that constants are used// therefore they cannot be changed.?>
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