PHP Learning notes _5_ array and predefined variables (not finished)

PHP has two types of arrays, indexed arrays and associative arrays, which are declared in a similar manner, mainly in the following three ways of declaring:

How to declare:
Array (); Can declare any array, see the following example

  
   1,2,3);    print_r($temp);//这是打印数组的方法/**    输出的结果，Array90    **/

Note the point:
1. Null to do the data key will be turned into an empty string;
2. When a new value is added, the array is labeled as the current maximum subscript plus 1, if the subscript maximum is negative, the index is 0 when an element with an unspecified index is added;
3.

$_POST：接收表单以POST发送的数据$_GET：接收表单以GET方式发送的数据$_REQUEST：$_GET+$_POST+$_COOKIE$_FILES：HTTP文件上传变量$_SERVER：服务器与执行环境变量$_ENV：环境变量$_SESSION：会话变量$_COOKIE：http cookie$_GLOBALE:预定义变量的总集合$php_errormsg：前一个错误信息（只在错误发生的作用域内可用，需要开启php.ini里track_error配置项）

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