Detailed explanation of getenv() function in php

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

getenv() function definition: Get the system environment variables;
Syntax: string getenv(string varname);
Note: What is returned is a string;

In PHP, the getenv(parameter) function is a function used to obtain environment variables. Different parameters can be obtained according to different parameters provided. environment variables.

The specific parameters are as follows:

"PHP_SELF"
The file name of the currently executing script is related to the document root.
If PHP is run in command line mode, this variable is invalid before PHP 4.3.0.

"argv"
The arguments passed to this script. When the script is run in command-line mode, the argv variable is passed to the program as C-style command-line arguments. When the GET method is called, this variable contains the requested data.

"argc"
Contains the number of command line arguments passed to the program (if running in command line mode).

"GATEWAY_INTERFACE"
The version of the CGI specification used by the server. For example, "CGI/1.1".

"SERVER_NAME"
The name of the server host where the script is currently running. If the script is running on a virtual host, the name is determined by the value set for that virtual host.

"SERVER_SOFTWARE"
The string of server identification is given in the header information when responding to the request.

"SERVER_PROTOCOL"
The name and version of the communication protocol when requesting the page. For example, "HTTP/1.0".

“REQUEST_METHOD”
Request method when accessing the page. For example: "GET", "HEAD", "POST", "PUT".
Note: If the request method is HEAD, the PHP script will abort after sending the header information (this means that after any output is generated, there is no more output buffering).

"REQUEST_TIME"
The timestamp when the request started. Valid since PHP 5.1.0.

"QUERY_STRING"
The string of query (the content after the first question mark? in the URL).

"DOCUMENT_ROOT"
The document root directory where the currently running script is located. Defined in the server configuration file.

"HTTP_ACCEPT"
The content of the Accept: header information of the current request.

"HTTP_ACCEPT_CHARSET"
The content of the Accept-Charset: header information of the current request. For example: "iso-8859-1,*,utf-8".

"HTTP_ACCEPT_ENCODING"
The content of the Accept-Encoding: header information of the current request. For example: "gzip".

"HTTP_ACCEPT_LANGUAGE"
The content of the Accept-Language: header information of the current request. For example: "en".

"HTTP_CONNECTION"
The content of the Connection: header information of the current request. For example: "Keep-Alive".

"HTTP_HOST"
The Host of the current request: the content of the header information.

"HTTP_REFERER"
The URL address of the previous page linked to the current page. Not all user agents (browsers) will set this variable, and some can also modify HTTP_REFERER manually. Therefore, this variable is not always true.

"HTTP_USER_AGENT"
The content of the User-Agent: header information of the current request. This string indicates information about the user agent accessing this page. A typical example is: Mozilla/4.5 [en] (X11; U; Linux 2.2.9 i586). This information can also be obtained using get_browser().

"HTTPS"
If the script is accessed through the HTTPS protocol, it is set to a non-empty value.

“REMOTE_ADDR”
The IP address of the user who is browsing the current page.

"REMOTE_HOST"
The host name of the user who is browsing the current page. Reverse domain name resolution is based on the user's
REMOTE_ADDR.
Note: The web server must be configured to create this variable. For example, Apache requires HostnameLookups On in httpd.conf. See gethostbyaddr().

"REMOTE_PORT"
The port used by users to connect to the server.

"SCRIPT_FILENAME"
The absolute path name of the currently executing script.
Note: If the script is executed in the CLI, as a relative path, such as file.php or ../file.php, $_SERVER[‘SCRIPT_FILENAME’] will contain the user-specified relative path.

"SERVER_ADMIN"
This value specifies the SERVER_ADMIN parameter in the Apache server configuration file. If the script is running on a virtual host, this value is that of that virtual host.

"SERVER_PORT"
The port used by the server. Default is "80". If using SSL secure connection, this value is the HTTP port set by the user.

"SERVER_SIGNATURE"
A string containing the server version and virtual host name.

"PATH_TRANSLATED"
The base path of the file system (not the document root directory) where the current script is located. This is the result after the server has been imaged from a virtual to real path.
Note: After PHP 4.3.2, PATH_TRANSLATED in Apache 2 SAPI mode is no longer implicitly assigned like Apache 1. Instead, if Apache does not generate this value, PHP will generate it itself and put its value into the SCRIPT_FILENAME server constant. middle. This modification complies with the CGI specification, which states that PATH_TRANSLATED only exists if PATH_INFO is defined.
Apache 2 users can use AcceptPathInfo On in httpd.conf to define PATH_INFO.

"SCRIPT_NAME"
Contains the path of the current script. This is useful when the page needs to point to itself. FILE Contains the absolute path and file name of the current file (such as an include file).

"REQUEST_URI"
The URI required to access this page. For example, "/index.html".

"PHP_AUTH_DIGEST"
When running as an Apache module, during the HTTP Digest authentication process, this variable is set to the "Authorization" HTTP header content sent by the client (so that for further authentication operations).

"PHP_AUTH_USER"
When PHP is running in Apache or IIS (PHP 5 is ISAPI) module mode and is using the HTTP authentication function, this variable is the user entered by the user name.

"PHP_AUTH_PW"
When PHP is running in Apache or IIS (PHP 5 is ISAPI) module mode and the HTTP authentication function is being used, this variable is the password entered by the user .

HTTP_CLIENT_IP
Get the user’s IP code;

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