PHP global variables and super global variable sharing

There are many superglobal variables in php, which means that they are available in the entire scope of a script. They can be accessed within a function or method without executing global $variable;.

These super global variables are:

• ##$GLOBALS References all variables available in the global scope

• $_SERVER This Superglobal variables hold information about headers, paths, and script locations.

• The most important elements that can be accessed in $_SERVER:
  Element/CodeDescription$_SERVER['PHP_SELF']Returns the file name of the currently executing script. $_SERVER['GATEWAY_INTERFACE']Returns the version of the CGI specification used by the server. $_SERVER['SERVER_ADDR']Returns the IP address of the server where the script is currently running. $_SERVER['SERVER_NAME']Returns the host name of the server where the script is currently running (such as www.w3school.com.cn). $_SERVER['SERVER_SOFTWARE']Returns the server identification string (such as Apache/2.2.24). $_SERVER['SERVER_PROTOCOL'] Returns the name and version of the communication protocol when the page was requested (for example, "HTTP/1.0"). $_SERVER['REQUEST_METHOD']Returns the request method used to access the page (such as POST). $_SERVER['REQUEST_TIME']Returns the timestamp when the request started (for example, 1577687494). $_SERVER['QUERY_STRING'] Returns the query string, if this page is accessed through the query string. $_SERVER['HTTP_ACCEPT'] Returns the request headers from the current request. $_SERVER['HTTP_ACCEPT_CHARSET']Return the Accept_Charset header from the current request (such as utf-8, ISO-8859-1)$_SERVER['HTTP_HOST']Return the Host header from the current request. $_SERVER['HTTP_REFERER']Returns the full URL of the current page (not reliable as not supported by all user agents). $_SERVER['HTTPS']Whether to query the script through the secure HTTP protocol. $_SERVER['REMOTE_ADDR']Returns the IP address of the user browsing the current page. $_SERVER['REMOTE_HOST']Returns the host name of the user browsing the current page. $_SERVER['REMOTE_PORT']Returns the port number used to connect to the web server on the user's machine. $_SERVER['SCRIPT_FILENAME']Returns the absolute path of the currently executing script. $_SERVER['SERVER_ADMIN']This value specifies the SERVER_ADMIN parameter in the Apache server configuration file. $_SERVER['SERVER_PORT']The port used by the Web server. The default value is "80". $_SERVER['SERVER_SIGNATURE'] Returns the server version and virtual host name. $_SERVER['PATH_TRANSLATED']The base path of the file system (not the document root directory) where the current script is located. $_SERVER['SCRIPT_NAME'] Returns the path of the current script. $_SERVER['SCRIPT_URI'] Returns the URI of the current page.
• $_REQUEST is used to collect data submitted by HTML forms.

• $_POST is used to collect form data after submitting the HTML form with method="post". $_POST is also commonly used to pass variables.

• $_GET is used to collect form data after submitting the HTML form (method="get").
  $_GET can also collect the data sent in the URL.

• $_FILES

• $_ENV

• $_COOKIE

• $_SESSION

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