PHP constants, what are PHP constants_PHP tutorial

php constants, what are php constants?

define() function is used to define constants. Once a constant is defined, it cannot be changed or undefined.

Example of defining constants:

<?php
define("CONSTANT", "码农教程");
echo CONSTANT;
?>

Run

Constant names follow the same naming rules as any other PHP tag. Legal constant names begin with a letter or an underscore, followed by any letters, numbers, or underscores.

Constants are case-sensitive by default. By convention, constant identifiers are always uppercase and the value cannot be changed during script execution.

The difference between defining constants and defining variables:

• There is no dollar sign ($) in front of the constant
• Constants can only be defined using the define() function, not assignment statements
• Constants can be defined and accessed anywhere regardless of variable scope rules
• Once defined, a constant cannot be redefined or undefined
• The value of a constant can only be a scalar

PHP has a large number of built-in predefined constants, please refer to the PHP manual for details.

Original address: http://www.manongjc.com/php/php_constant.html

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