PHP Constants

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Constants are variables
Constants are variables except that once they are defined they can’t be changed or undefined.

  • A constant is an identifier (name) for a simple value. The value cannot be changed during the script.
  • A valid constant name starts with a letter or underscore.
  • (no $ sign before the constant name).
  • Note: Unlike variables, constants are automatically global across the entire script.

Create a PHP constant

  • You can create a constant by using the define () function.
  • Use the define function to specify the name and value of a constant. (name, value, case-insensitive).
  • Many programmers use capital letters to name constants – so they stand out.
  • Note: Since a constant can not be change you do not use a $ sign before it’s name when you declare it or (use it).


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

How to declare constants

PHP Constant Examples

Output: Welcome to!



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