Redirect in PHP

Redirect is a technology often used in web development, which allows us to redirect users from the current URL address to another URL address. In PHP, redirection is implemented through the header() function.

The header() function can output HTTP header information, including redirection information. We can redirect the user to another URL address by using the header() function, as shown below:

header("Location: http://www.example.com");

When we execute the above code, the server will send an HTTP response to the client, which contains the redirection information. The client browser will automatically redirect to the specified URL based on the response.

When using the header() function, you need to pay attention to the following points:

1. The header() function must be called before all other output, otherwise an error will be generated.
2. Before calling the header() function, there cannot be any output, including spaces and newlines, etc.
3. If you need to continue outputting content after the header() function, you must first call the ob_start() function. This function will open an output buffer, and all output will be temporarily stored in the buffer until the buffer is explicitly flushed or closed.

Let’s look at a specific example:

ob_start();
header("Location: http://www.example .com");
ob_end_flush();
?>

In the above example, we first call the ob_start() function to open an output buffer. Then, we call the header() function to redirect the user to the http://www.example.com address. Finally, we call the ob_end_flush() function to output the contents of the buffer to the client.

In addition to using the header() function directly, PHP also provides a more convenient function header_redirect(). This function works like the header() function, but is more convenient to use. The usage of the header_redirect() function is as follows:

header_redirect("http://www.example.com", true, 301);

This function accepts three parameters: the redirected URL address, whether the HTTP response status code needs to be set, and the value of the HTTP response status code. We can specify the HTTP response status code to be used in the parameters, such as 301 for permanent redirection, 302 for temporary redirection, etc.

When using the header_redirect() function, you need to pay attention to the following points:

1. The header_redirect() function also needs to be called before all other output.
2. If you need to redirect to a local URL address, you must use an absolute path, such as /header.php instead of ./header.php.
3. The HTTP response status code defaults to 302. If you do not need to specify the response status code, you can set the second parameter to false.

To sum up, redirection is an indispensable technology in web development. In PHP, we can use the header() function or header_redirect() function to implement the redirection function. No matter which method is used, certain rules and precautions need to be followed to ensure the effectiveness and correctness of redirection.

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