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PHP headers_list() function (with example)

Hey everyone,

I've been working with PHP recently and came across the `headers_list()` function. I'm a bit confused about what it does and how it works.

I saw that `headers_list()` is a built-in PHP function that returns a list of headers that have been sent to the browser. But I'm not sure how and when these headers are sent, and what exactly they contain.

Can someone explain how the `headers_list()` function works in PHP? Maybe provide a simple example to help me understand better?

Any help would be greatly appreciated!


All Replies



I can share my experience with using `headers_list()` in PHP as well!

`headers_list()` is a handy function that allows you to inspect the headers sent from the server to the client. One interesting use case I had was when I needed to debug an issue with caching.

In my situation, I had implemented caching for certain API responses using the `Cache-Control` header. I was initially unsure if the headers were being set correctly, so I used `headers_list()` to check the headers that were being sent.

To check the headers, I added the following code snippet after the relevant caching logic:

$headers = headers_list();

foreach ($headers as $header) {
echo $header . "<br>";

This code displayed all the headers sent for that specific request. By examining the headers, I could verify if my caching headers were set correctly and whether the browser was properly caching the responses.

In addition to this, `headers_list()` can be useful in scenarios where you need to ensure certain headers are sent or to debug unexpected headers being sent.

Overall, `headers_list()` is a nifty function that can help you inspect the headers sent to the browser during a PHP request. You can use it to troubleshoot issues, validate header configurations, or simply gain better insight into the HTTP responses.

Feel free to ask if you have any further questions or need additional examples!

Best regards.


Hello there,

I've had some personal experience working with `headers_list()` in PHP, and I thought I could share my insights with you.

One of the scenarios where I found `headers_list()` particularly useful was when I wanted to check the redirects happening during a request. Sometimes, when dealing with complex applications or frameworks, there might be situations where multiple redirects occur in the process of serving a page.

To understand the redirect flow and how headers are being handled, I used `headers_list()` in combination with the `header()` function. By making use of the `header()` function and specifying a custom "Location" header, I was able to simulate a redirect within my PHP script.

Here's an example:

header("Location: /newpage.php");

By using this code snippet, I could observe the headers being sent during the redirect process. Then, I would follow it up with `headers_list()`, which provided me with the list of headers to inspect.

With the help of `headers_list()`, I could verify if the appropriate headers were being set, such as the "Location" header in this case. It enabled me to ensure that the redirection was working as expected and allowed me to troubleshoot any potential issues.

Additionally, `headers_list()` can be beneficial when debugging authentication or authorization scenarios, as it helps to examine the headers involved in the authentication process.

I hope my personal experience shed some light on how `headers_list()` can be useful. Let me know if you have any further questions!

Best regards.


Hey there,

I've used `headers_list()` before, so I can help you out with some more information!

The `headers_list()` function indeed returns an array containing all the headers that have been sent to the browser during the current request. These headers are part of the HTTP response sent from the server to the client (usually a web browser).

Headers contain important information about the response, such as the content type, caching instructions, cookies, and more. They are used to provide additional instructions or metadata to the browser or other client applications.

To give you an example, let's say you have a PHP script that generates a JSON response. You might want to set the `Content-Type` header to `application/json` to let the client know that it's receiving JSON data. You can use the `header()` function to set this header before sending any output:

header("Content-Type: application/json");

Later in your script, if you want to check what headers have been sent, you can use the `headers_list()` function like this:

$headers = headers_list();

foreach ($headers as $header) {
echo $header . "<br>";

This will output all the headers that have been sent during the current request.

Keep in mind that `headers_list()` only displays the headers that have already been sent, so make sure to call it after you have sent any headers using the `header()` function.

I hope this clarifies things a bit for you. Let me know if you have any further questions!


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