The difference between php variables and constants

Constant:

Identifier used to store a data that will not change and is not expected to change (the naming rules are the same as variables)

Definition form: (Recommended learning: PHP video tutorial)

Use define() function definition

Use form: define ("Constant name", constant value)

Use counst syntax definition

Usage form: counst constant name = constant value

Use constants: There are two forms 1. Use the name directly 2. Use the constant() function: constant ("constant name")

Use constants: There are two forms 1. Use the name directly 2. Use the constant () function: constant ("constant name")

The difference between constants and variables:

Definition form Different (php variables have no defined keywords or functions and are defined when assigning values. PHP constants must be defined using the define() function);

The usage form is different (constants do not require the $ symbol);

Different degrees of variability (the value of a constant cannot be changed or destroyed);

Different scopes (constants have super-global scope (can be used directly inside and outside the function));

The available types are different (constants can only store scalar types: int, float, string, bool);

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