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This article focuses on "how to deal with PHP super global variables", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to deal with PHP super global variables.

PHP super global variable

Global variables defined outside the function cannot be referenced inside the function, but sometimes they need to be used within the function, so super global variables can be referenced inside the function.

Several super global variables are predefined in PHP, which means that they can be referenced in all scopes of a script. Super global variables can be used in functions and classes without special instructions.

PHP super global variable:

$GLOBALS

$_ SERVER

$_ REQUEST

$_ POST

$_ GET

$_ FILES

$_ ENV

$_ COOKIE

$_ SESSION

Today, let's take a look at several super global variables commonly used in daily use, and then let's take a look at some examples of their usage and features.

First of all, let's take a look at:

PHP $GLOBALS

$GLOBALS is a predefined hyperglobal array that contains all available variables in the global scope, and the name of the variable is the key of the array. GLOBALS is accessible in all scopes of a PHP script.

Examples are as follows:

Output result:

$GLOBALS is not limited to be used within the function and can be used anywhere in the program. As you can see from the above example, the global variable becomes a super global variable so that it can be accessed normally inside the function.

Global

There is also a global keyword that is very similar to $GLOBALS, which also allows us to use global variables defined outside the function inside the function.

The syntax format is as follows:

Global variable 1, variable 2,...

The global keyword can be followed by multiple variables as parameters, separated by "," (comma). At the same time, there are some key points to pay attention to when using global:

The global keyword, which cannot be used outside the function, can only be used inside the function

The global keyword can only be used to refer to global variables outside the function, and cannot be assigned directly when referencing. Assignment and declaration statements need to be written separately.

When a variable modified with the global keyword is destroyed inside the function, the variables outside the function are not affected.

Examples are as follows:

In the above example, three variables are defined, but the global keyword modifies only two variables within the function, so what is the effect of the output?

Output result:

As you can see, the result only outputs variables an and b, because the global keyword only modifies two in the function, so the variable c is not used successfully.

Through two examples, we can see that compared with global, $GLOBALS has the following differences:

Global $refers to a reference to a variable of the same name outside the function, which is two variables that do not affect each other, while $GLOBALS [] refers to the external variable of the function itself, which is a variable.

$GLOBALS is not limited to be used within the function and can be used anywhere in the program.

PHP $_ SERVER

PHP $_ SERVER is exactly an array, and $_ SERVER contains header information, path, script location, and so on. The items in this array are created by the Web server. The server may ignore some, and not necessarily every server provides all the items.

Let me give you an example of how to use PHP $_ SERVER:

Output result

To share with you, more important elements in the $_ SERVER variable:

$_ SERVER ['PHP_SELF']-the file name of the currently executed script, related to document root.

$_ SERVER ['GATEWAY_INTERFACE']-the version of the CGI specification used by the server.

$_ SERVER ['SERVER_ADDR']-the IP address of the server on which the script is currently running.

$_ SERVER ['SERVER_NAME']-the hostname of the server on which the script is currently running.

$_ SERVER ['SERVER_SOFTWARE']-the server identity string, given in the header information when responding to the request.

$_ SERVER ['SERVER_PROTOCOL']-the name and version of the communication protocol when the page is requested.

$_ SERVER ['REQUEST_METHOD']-the request method used to access the page.

$_ SERVER ['REQUEST_TIME']-the timestamp at the start of the request. Available since PHP 5.1.0.

$_ SERVER ['QUERY_STRING']-query string (query string), which is used to access the page, if any.

$_ SERVER ['HTTP_ACCEPT']-the content of the Accept: item in the current request header, if it exists.

$_ SERVER ['HTTP_ACCEPT_CHARSET']-the content of the Accept-Charset: item in the current request header, if it exists.

$_ SERVER ['HTTP_HOST']-the content of the Host: item in the current request header, if it exists.

$_ SERVER ['HTTP_REFERER']-directs the user agent to the address of the previous page of the current page, if any.

$_ SERVER ['HTTPS']-if the script is accessed through the HTTPS protocol, it is set to a non-empty value.

$_ SERVER ['REMOTE_ADDR']-the IP address of the user browsing the current page.

$_ SERVER ['REMOTE_HOST']-the hostname of the user browsing the current page. DNS reverse parsing does not depend on the user's REMOTE_ADDR.

$_ SERVER ['REMOTE_PORT']-the port number used to connect to the Web server on the user's machine.

$_ SERVER ['SCRIPT_FILENAME']-the absolute path to which the script is currently executed.

$_ SERVER ['SERVER_ADMIN']-this value indicates the SERVER_ADMIN parameter in the Apache server configuration file. If the script runs on a virtual host, this value is the value of that virtual host.

$_ SERVER ['SERVER_PORT']-the port used by the Web server. The default is "80". If you use a SSL secure connection, this value is the HTTP port set by the user.

$_ SERVER ['SERVER_SIGNATURE']-contains a string of server version and virtual hostname.

$_ SERVER ['PATH_TRANSLATED']-the basic path to the file system (not the document root) on which the current script resides. This is the result after the server makes a virtual image to the real path.

$_ SERVER ['SCRIPT_NAME']-contains the path to the current script. This is useful when the page needs to point to itself. The _ _ FILE__ constant contains the full path and file name of the current script, such as an include file.

$_ SERVER ['SCRIPT_URI']-URI is used to specify the page to visit. For example, "/ index.html".

At this point, I believe you have a deeper understanding of "how to deal with PHP super global variables". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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