PHP Learning--Basic knowledge summary

One: PHP variables

1. Seven major variable types

   Integer, Float, String, Array, object, NULL, resource.

2. Scope of the variable
   Local, Global
   Built-in Super global variables:
   $GLOBALS 、所有全局变量的数组
$_SERVER、服务器环境变量数组
$_GET、通过GET方法传递给该脚本的变量数组
$_POST、通过POST方法传递给该脚本的变量数组
$_COOKIE、cookie变量数据
$_FILES、与文件上传相关的变量数组
$_ENV、环境变量数组
$REQUEST、所有与用户输入的变量数组
$SESSION、会话变量数组


3. Variable detection function
   Is_xxx (), is a variable of type XXX

4. State detection of variables
   Isset (): Whether the variable is set
   Unset (): Destroying variables
   Empty (): detects if a variable exists, and whether its value is null and not 0

5. Constant definition
   define('常量名'，'常量值')；

Two: operator

1. Arithmetic operators
2. String operator
3. Assignment operator
4. Comparison operators
5. logical operators
6. Bitwise operators
7. Other operators
   Ternary operator, error suppressor @, type operator instanceof

Three: Logical Structure

1. Select structure
If, If~else, switch~case
2. Cyclic structure
While, for, foreach

Summary picture

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