Learn superglobal variables in php

Since PHP 4.2.0, the default value of register_globals is off. Therefore, many variables that can be used directly in the past, such as $PHP_SELF or the set SESSION variable, cannot be accessed in the form of "$variable name", which may cause problems. A lot of inconvenience, but it helps improve safety.

Since PHP 4.2.0, the default value of register_globals is off. Therefore, many variables that can be used directly in the past, such as $PHP_SELF or the set SESSION variable, cannot be accessed in the form of "$variable name", which may cause It brings a lot of inconvenience, but it helps improve safety. To access these variables, you need to use PHP superglobal variables, as follows:

$_SERVER Variables are set by the web server or are directly associated with the execution environment of the current script. Similar to the old $HTTP_SERVER_VARS array. The previous $PHP_SELF corresponds to $_SERVER['PHP_SELF']. You can use phpinfo to view your $_SERVER variable.

$_GET Variables submitted to the script via the HTTP GET method. Similar to the old $HTTP_GET_VARS array.

$_POST Variables submitted to the script via the HTTP POST method. Similar to the old $HTTP_POST_VARS array.

$_COOKIE Variables submitted to the script via the HTTP Cookies method. Similar to the old $HTTP_COOKIE_VARS array.

$_SESSION Variables currently registered for the script session. Similar to the old $HTTP_SESSION_VARS array.

$_FILES Variables submitted to the script via HTTP POST file upload. Similar to the old $HTTP_POST_FILES array.

$_ENV Variables submitted to the script by the execution environment. Similar to the old $HTTP_ENV_VARS array.

For the $_FILES variable: (the file domain field is "myfile")

$_FILES['myfile']['name'] The original name of the client machine file (including path).

$_FILES['myfile']['type'] The MIME type of the file, which requires browser support for this information, such as "image/gif".

$_FILES['myfile']['size'] The size of the uploaded file, in bytes.

$_FILES['myfile']['tmp_name'] The temporary file name (including path) stored on the server after the file is uploaded.

$_FILES['myfile']['error'] Error code related to the file upload. ['error'] was added in PHP 4.2.0.

When register_globals in php.ini is set to on, $myfile_name is equivalent to $_FILES['myfile']['name'], $myfile_type is equivalent to $_FILES['myfile']['type'], etc. .