A constant is a name or an identifier for a simple value. A constant value cannot change during the execution of the script. A constant name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.
PHP constant : define()
Let's see the syntax of define() function in PHP.
define(name, value, case-insensitive)
name : specifies the constant name
value : specifies the constant value
case-insensitive : Default value is false. It means it is case sensitive by default.
