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CGI environment variables

Lecture



Immediately before running the script, the server sends it some environment variables with information. Certain variables contain some headers, but, as already mentioned, not all (you cannot get all the headers). Environment variables in the PHP language can be used as the most ordinary variables. Environment variables are divided into four large groups:

  • Variables generated by the server;
  • Apache server special variables;
  • HTTP request field variables;
  • SSL connection variables (secure connection).

Consider the first three groups of environment variables:

Variables generated by the server:

Environment variable
Description of the environment variable
AUTH_TYPE The authentication scheme is used. Usually 'BASIC'
CONTENT_LENGTH Content length, for example, text / html
CONTENT_TYPE MIME content type, for example, text / html
GETAWAY_INTERFACE CGI version, for example CGI / 1.1
PATH_INFO HTTP script path
PATH_TRANSLATED Full path to the script
REMOTE_ADDR IP address of the requested client computer
REMOTE_HOST The domain name of the requesting computer (if available). The domain name is determined by the web server using DNS. Apache's HostNameLookups directive allows (or denies) the conversion of an IP address to a domain name.
REMOTE_PORT Port assigned to the browser to receive a response from the server
REMOTE_USER Authenticated username
QUERY_STRING The string of parameters passed to the server
SERVER_ADDR Server ip address
SERVER_NAME The domain name of the server. Determined by the ServerName directive of the configuration file
SERVER_PORT TCP port of the web server. Usually 80
SERVER_PROTOCOL HTTP protocol version. For example, HTTP / 1.1
SERVER_SOFTWARE Server software
SCRIPT_NAME HTTP script path
SCRIPT_FILENAME The file name of the script in the server file system (physical path). For example, /var/www/cgi-bin/script.cgi

Apache server special variables:

Environment variable
Description of the environment variable
DOCUMENT_ROOT The physical path to the root www-directory of the server. For example, /var/www.html/
SERVER_ADMIN Server Admin Email
SERVER_SIGNATURE Server signature For example, "Apache / 1.3.3 Server at www.somefirm.com Port 80"

HTTP request field variables:

Environment variable
Description of the environment variable
HTTP_HOST The name of the virtual host to which the request is addressed.
HTTP_USER_AGENT Remote user software. Usually this environment variable contains the name and version of the browser.
HTTP_ACCEPT List of supported client content types. Recently, instead of a list, browsers return the value *. *, Which means "all types"
HTTP_ACCEPT_LANGUAGE List of supported languages ​​in order of preference, for example, ru, en
HTTP_ACCEPT_ENCODING List of supported compression methods
HTTP_ACCEPT_CHARSET List of supported encodings
HTTP_CONNECTION

Connection type. Two options are possible:

  • Keep-alive - if, after responding to a request, you do not need to break the connection;
  • Close - if you need to close the connection immediately after responding to the request.
HTTP_REFERER The value of the REFERER field. In this field, the browser sends the URL of the resource that refers to our server. For example, if a user navigates to the site from http://www.somehost.com/page.php, then the value of the REFERER field will be http://www.somehost.com/page.php.
HTTP_X_FORWARDED_FOR If the user is working through a proxy server, then this field will contain the IP address of the computer accessing the proxy server. If this field already contains a value, then the new value will be added separated by commas.

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Running server side scripts using PHP as an example (LAMP)

Terms: Running server side scripts using PHP as an example (LAMP)