PHP data types

The content of this article mainly introduces the data types of PHP, which has certain reference value. Now I share it with everyone. Friends in need can refer to it

There are eight data types in PHP

• can be divided into three categories

1. Scalar: floating point, integer, character String, Boolean

2. Composite: array, object

3. Special: null, resource

• Floating point types must not be used in equality judgments. There will be loss when the computer converts to binary calculations

• Boolean type

• False seven situations: 0, 0.0, ' ', '0', false, array()//empty array, NULL

• ##Array type

Super global array $GLOBALS, $_GET, $_POST, $_REQUEST, $_SESSION, $_COOKIE, $_SERVER , $_FILES, $_ENV

Detailed explanation of $_SERVER: http://php.net/manual/zh/reserved.variables.server.php

##NULL three types Situation: Direct assignment to NULL, undefined variables, variables destroyed by unset
Constant
Definition method: const, define

    define('P1',"hello");    const P2 = "world";

const is faster, it is a language structure, define is a function; const can be used for the definition of class constants, define cannot

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