Detailed explanation of variables_order parameter

Detailed explanation of variables_order parameter

● $_ENV in PHP is an array containing server-side environment variables. It is a super global variable in PHP and we can directly access it anywhere in the PHP program.

● $_ENV just passively accepts server-side environment variables and converts them into array elements. You can try to output it directly.

● When you want to see what is in a variable, there are three ways I know:

1, var_dump($_ENV);

2、print_r($_ENV);

3、foreach($_ENV as $key=>$val){echo $key. '--------'.$val.'<br>';}

● Among these three methods, the first one I think is the most convenient and output content format clear.

● Since the $_ENV variable depends on the environment variable of the server, the results printed by the $_ENV variable obtained from different servers may be completely different. So it is not possible to list a complete list like $_SERVER. The following are the more common elements contained in the $_ENV array:

● Sometimes, $_ENV will be empty. The reason is usually that the configuration item of the php configuration file php.ini is: variables_order = "GPCS". To make the value of $_ENV not empty, the value of variables_order should be added with a capital letter "E", that is: variables_order = "EGPCS".

● The above configuration represents the source and order of external variables accepted by PHP. EGPCS is the abbreviation of Environment, Get, Post, Cookies, and Server. If E is missing from the configuration of variables_order, PHP cannot accept environment variables, and $_ENV will be empty.

● Since turning on $_ENV, that is, variables_order = "EGPCS" will cause some performance losses, according to PHP officials, it is not recommended in production environments. They prefer to use the getenv (string $varname) function to obtain the value in Environment, and this needs to be noted when programming. If $_ENV is used during programming and variables_order is not configured as variables_order = "EGPCS", an error may be reported when the program is run.

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