Summary of various methods of php predefined variables_PHP tutorial

PHP provides a large number of predefined variables. Detailed documentation is not available as many variables depend on the version and settings of the running server, among other factors. Some predefined variables do not take effect when PHP is run from the command line. Detailed list of these variables

User-defined predefined variables

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echo "当前操作系统信息".PHP_OS." "; echo '本文件路径和文件名为：'.__FILE__.' '; echo "当前PHP版本信息".PHP_VERSION." "; ?>

echo "Current operating system information".PHP_OS."
";
echo 'The path and file name of this file are:'.__FILE__.'
';
echo "Current PHP version information".PHP_VERSION."
";
?>

System predefined variables

$GLOBALS
Contains a reference to a globally valid variable in each current script. The key names of this array are the names of global variables. The $GLOBALS array exists since PHP 3.

$_SERVER
Variables are set by the web server or directly associated with the execution environment of the current script. Similar to the old $HTTP_SERVER_VARS array (still valid, but deprecated).

$_GET
Variables submitted to the script via URL requests. Similar to the old $HTTP_GET_VARS array (still valid, but deprecated).

$_POST
Variables submitted to the script via the HTTP POST method. Similar to the old $HTTP_POST_VARS array (still valid, but deprecated).

$_COOKIE
Variables submitted to the script via the HTTP Cookies method. Similar to the old $HTTP_COOKIE_VARS array (still valid, but deprecated).

$_FILES
Variables submitted to the script via HTTP POST file upload. Similar to the old $HTTP_POST_FILES array (still valid, but deprecated). See POST method upload for details.
$_ENV
Variables submitted to the script by the execution environment. Similar to the old $HTTP_ENV_VARS array (still valid, but deprecated).

$_REQUEST
Variables submitted to the script via GET, POST and COOKIE mechanisms, so this array is not trustworthy. The presence, absence, and order of all variables contained in this array are defined according to the variables_order configuration directive in php.ini. This array has no direct counterpart prior to PHP 4.1.0. See import_request_variables().

As of PHP 4.3.0, file information in $_FILES no longer exists in $_REQUEST.

Note: When running in command line mode, this array will not contain the argv and argc entries; they are already present in the array $_SERVER.

$_SESSION
The variables currently registered for the script session. Similar to the old $HTTP_SESSION_VARS array (still valid, but deprecated).

$_SERVER['PHP_SELF']

The file name of the currently executing script, related to the document root. For example, using $_SERVER['PHP_SELF'] in a script with the URL address http://example.com/test.php/foo.bar will result in /test.php/foo.bar. This variable has no effect if PHP is run from the command line.

$_SERVER['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. For example, at the URL address /test.php $_SERVER['SERVER_NAME'] will get this result.

Example

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// user sent a GET header with key = secret_access, val = true, so echo $_GET["secret_access"]; // output: true echo $secret_access; // output: session_start(); // in previous logic, you set session variable $secret_access = false echo $_SESSION["secret_access"]; // output: false echo $secret_access; // output: false extract_globals(); // Globals put into "normal" variables echo $_GET["secret_access"]; // output: true echo $_SESSION["secret_access"]; // output: false echo $secret_access; // output: true // VARIABLES ARE COMPROMISED! // DO NOT USE $secret_access ! // USE $_SESSION["secret_access"] instead !!! ?>

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// user sent a GET header with key = secret_access, val = true, so

echo $_GET["secret_access"]; // output: true echo $secret_access; // output: session_start(); // in previous logic, you set session variable $secret_access = false echo $_SESSION["secret_access"]; // output: false echo $secret_access; // output: false extract_globals(); // Globals put into "normal" variables

echo $_GET["secret_access"]; // output: true

echo $_SESSION["secret_access"]; // output: false