How to use curl to follow jump in php

PHP is a programming language widely used in back-end development, and cURL is one of the most important extensions, providing access to the World Wide Web and other application services. When using cURL, following jumps is one of the very useful features. This article will explain how to use cURL in PHP to follow redirects.

1. What is follow jump

Follow jump, also known as automatic redirection, refers to whether the client is redirected after redirection in the HTTP request. Automatically request the new URL that leads to, rather than manually requesting it. In web applications, you may need to use follow jumps for various reasons (such as server load balancing, redirection, login, etc.). If the request does not have follow-through enabled, the client application will return to processing. At this point, the redirect needs to be handled manually (programmatically).

2. Use cURL to follow the jump

cURL is an open source client, library and toolset that supports various network alternatives. HTTP requests can be made using the cURL library, therefore, we can use it to get redirect URLs, or follow and handle redirects that have already occurred.

1. Enable follow redirects

When using cURL, redirects will not be followed by default. To enable the follow redirect function, you can use the curl_setopt() function and pass its second parameter CURLOPT_FOLLOWLOCATION to set it.

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://example.com/");
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_exec($ch);
curl_close($ch);

2. Get the redirect URL

You can easily capture the redirect URL using cURL as shown below:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://example.com/");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_NOBODY, true);
$response = curl_exec($ch);
$redirectedUrl = curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);
curl_close($ch);

In the above code, CURLOPT_RETURNTRANSFER is set to true This is to convince cURL to return a response instead of outputting it directly. The function of these two parameters, CURLOPT_HEADER and CURLOPT_NOBODY, is to process the request header. The curl_getinfo() function provides a lot of information about cURL resources, such as CURLINFO_EFFECTIVE_URL for getting the redirected URL. A previously created cURL session must be used with this function when calling this function.

3. Precautions

When using cURL’s follow redirect function, you need to pay attention to the following matters:

1. By default, cURL doesn't follow redirects. Only when the CURLOPT_FOLLOWLOCATION parameter of the curl_setopt function is set to true will cURL follow the redirect.
2. You also need to pay attention to some issues when capturing the redirect URL, such as whether you need to call the curl_close() function to close the session after processing.
3. Due to different network environments, problems such as the failure of the follow jump function may occur. Therefore, it is necessary to master the use of this function flexibly in practice.

4. Summary

This article introduces the follow jump function using cURL. This is a very practical technology that is often used in many Web applications. in process. Although the use of cURL is relatively complicated, a careful understanding and use of it will definitely be of great help to the work of web developers.

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