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:
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.
Note: Unlike variables, constants are automatically global throughout the script.
PHP constant: define()
Use the define() function to create a constant. It defines constant at run time. Let's see the syntax of define() function in PHP.
Let's see the example to define PHP constant using define().
Hello JavaTpoint PHP
Create a constant with case-insensitive name:
Hello JavaTpoint PHP Hello JavaTpoint PHP
Hello JavaTpoint PHP Notice: Use of undefined constant message - assumed 'message' in C:\wamp\www\vconstant3.php on line 4 message
PHP constant: const keyword
PHP introduced a keyword const to create a constant. The const keyword defines constants at compile time. It is a language construct, not a function. The constant defined using const keyword are case-sensitive.
Hello const by JavaTpoint PHP
There is another way to print the value of constants using constant() function instead of using the echo statement.
The syntax for the following constant function:
Constant vs Variables