Detailed explanation of the meaning and usage of define in php

define() function understanding 1(focus on understanding the function)

define() function defines a constant.

Characteristics of constants:

Constants are similar to variables. The difference is: after setting, the value of the constant cannot be changed. The constant name does not need the dollar sign ($) at the beginning. The scope Does not affect access to constants, constant values can only be strings or numbers.

define function understanding 2(focus on parameter understanding)

Grammar:

define(name,value,case_insensitive)

Parameter description:

name is required. Specifies the name of the constant. //The name parameter is the first parameter of the define function and is in uppercase;

value is required. Specifies the value of the constant. //The value of value is generally a string or number

case_insensitive

optional. Specifies whether constant names are case-sensitive.

If set to true, it will not be case sensitive. Default is false (case sensitive).

define function understanding 3(focus on example understanding)

Question 1: A case-sensitive constant:

The output result is: Hi Friend!

Note: Enter the symbols accurately, otherwise it is easy to make mistakes

## define function understanding 4

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