Redirect tutorial in PHP-PHP Tutorial-php.cn

Redirect tutorial in PHP

王林

Release： 2023-09-01 17:54:01

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1426 people have browsed it

Redirect allows you to redirect the client browser to a different URL. You can use it when switching domains, changing your site structure, or switching to HTTPS.

In this article, I will show you how to redirect to another page using PHP. I'll explain exactly how PHP redirects work and show you what's happening behind the scenes.

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How does basic redirection work?

Before we dive into the details of PHP redirection, let’s take a quick look at how HTTP redirection actually works. Take a look at the image below.

Redirect tutorial in PHP

Let’s understand what’s going on in the screenshot above:

The client browser requests a specific page from the server. In the example above, the client requested the contents of the index.php file.
The server received a request for the index.php file and wishes to notify the client that the file is no longer available or has been moved to a different location, and that it should look for a new file: new_index.php. PHP. The server sends the Location header with the new URL and a 301 or 302 HTTP code. These are the HTTP codes used for redirects.
When the client browser encounters a 301 or 302 code, it knows that it must make another request to the new URL to get the content. It makes a request to get the new_index.php file in the example above.
Finally, the server sends the contents of the new URL.

This is how basic HTTP redirection works. In the next section, we will discuss how PHP redirection works.

How Redirects Work in PHP

In PHP, when you want to redirect a user from one page to another, you need to use the header() function. The header function allows you to send a raw HTTP location header, which performs the actual redirection we discussed in the previous section.

How to use the header function

Let's take a look at the syntax of the header() function.

header( $header, $replace, $http_response_code )

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$header: This is the HTTP header string you want to use. In our case, we will use the Location header for redirection.
$replace: This is an optional parameter indicating whether the header should replace a previous similar header.
$http_response_code: It allows you to send a specific response code.

Now, let’s look at the following examples to see how they work together.

<?php
// index.php
header("Location: https://www.yoursite.com/new_index.php");
exit();
?>

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When the above script is executed, the client browser will be redirected to http://www.yoursite.com/new_index.php. Behind the scenes, it sends the raw HTTP Location header along with a 302 status code. The 302 status code is used for temporary redirects, but if you want a permanent redirect, you can pass a 301 status code in the third parameter as shown in the following code snippet.

<?php
// index.php
header("Location: http://www.yoursite.com/new_index.php", TRUE, 301);
exit();
?>

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301 Permanent redirects allow you to notify search bots that the page is no longer available and can be replaced with a new page.

Why use the `Die()` or `Exit()` function after a header redirect?

Eagle-eyed users will notice that I used the exit() function in the above example. In fact, you must use the exit() or die() function immediately after the header redirection to stop script execution and avoid any undesirable results.

Therefore, it is always recommended to use one of these functions after a redirect.

Notable Error: Header Sent

If you are an experienced PHP programmer, I am sure that you have encountered this famous PHP error at some point in your daily PHP development. However, for beginners, encountering this error is really annoying as it is difficult to debug and fix. In most cases, they don't even know it's caused by a header redirect.

The rule of thumb is that when you use the header() function in a script, you need to make sure no output is sent before it. Otherwise, PHP will complain with a "Header Sent" error. This can happen even if you send a space before using the header function.

in conclusion

In this article, we discussed one of the important features of PHP programming: redirection. First, we looked at the basics of HTTP redirection and then demonstrated how it works in PHP.

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Redirect tutorial in PHP