Execute a HTTP POST Using PHP CURL

Introduction

In this article, we're going to show you how to use the cURL library in PHP to make a non-traditional HTTP POST request.

A Quick Look at Application

A customer recently brought to me a unique challenge. My customer wants information requests from data to be collected in a database. Nothing new, right? Well, there's a hurdle — the information isn't going to be saved on the localhost database — it needs to be stored in a remote database that I cannot connect directly to.

I thought about all of the possible solutions for solving this challenge and settled on this flow:

1. User will submit the form, as usual.
2. In the form processing PHP, I use CURL to execute a POST transmission to a PHP script on the customer's server.
3. The remote script would do a MySQL INSERT query into the customer's private database.

This solution worked quite well so I thought I'd share it with you. Here's how you execute a POST using the PHP CURL library.

//extract data from the postextract($_POST);
//set POST variables
$url = 'http://domain.com/get-post.php';
$fields = array('lname'=>urlencode($last_name),
                'fname'=>urlencode($first_name),
                'title'=>urlencode($title),
                'company'=>urlencode($institution),
                'age'=>urlencode($age),
                'email'=>urlencode($email),
                'phone'=>urlencode($phone)
                );

//url-ify the data for the POST
foreach($fields as $key=>$value) { 
	$fields_string .= $key.'='.$value.'&'; 
 }
 rtrim($fields_string,'&');
 //open connection
 $ch = curl_init();
 
 //set the url, number of POST vars, POST data
 curl_setopt($ch,CURLOPT_URL,$url);
 curl_setopt($ch,CURLOPT_POST,count($fields));
 curl_setopt($ch,CURLOPT_POSTFIELDS,$fields_string);

//execute post
$result = curl_exec($ch);

//close connection
curl_close($ch);

How would you have solved this problem?

What is cURL?

cURL, pronounced "see URL," stands for "client URL." cURL is a software library that lets you transfer data using various protocols, including HTTP, FTP, and SMTP. cURL is widely used because the program supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, Kerberos, HTTP form-based upload, proxies, cookies, and user+password authentication.

cURL is available for free and runs on many different operating systems, including Windows, Linux, MAC OS X, and more.

How to install cURL?

To use cURL in PHP, you must have the cURL library installed on your web server. This can be done using a package manager such as apt-get on Linux or Homebrew on MAC OS X. 

Once cURL is installed, you can use the phpinfo() function to verify that the cURL extension is enabled. To install on a Windows machine, you can download cURL from here and find instructions here. 

How to use cURL?

cURL can be employed to make HTTP requests in a number of different ways. For example, you can use cURL to make an HTTP GET request or an HTTP POST request.

cURL is a great tool for making HTTP requests because it's easy to use and supports a variety of protocols. cURL can be used to make HTTP requests in a number of different ways, including GET and POST requests. Additionally, cURL supports SSL certificates, proxies, cookies, and user+password authentication. This makes cURL an ideal tool for making HTTP requests in a variety of different situations.

How to make an HTTP POST request using cURL?

To make an HTTP POST request using cURL, you need to use the -d option (for data). The -d option allows you to specify data to be sent in the HTTP request body. For example, to make an HTTP GET request using cURL, you can use the following syntax:

$ curl -X GET <URL> 

For example, to make a GET request to the Google homepage, you can use the following command:

$ curl -X GET https://www.google.com 

How to make an HTTP POST request using cURL?

To make an HTTP POST request using cURL, you can use the following syntax:

$ curl -X POST <URL> 

For example, to make a POST request to the Google homepage, you can use the following command:

$ curl -X POST https://www.google.com 

How to make an HTTP PUT request using cURL?

To make an HTTP PUT request using cURL, you can use the following syntax:

$ curl -X PUT <URL> 

For example, to make a PUT request to the Google homepage, you can use the following command:

$ curl -X PUT https://www.google.com 

How to make an HTTP DELETE request using cURL?

To make an HTTP DELETE request using cURL, you can use the following syntax:

$ curl -X DELETE <URL> 

For example, to make a DELETE request to the Google homepage, you can use the following command:

$ curl -X DELETE https://www.google.com 

How to make an HTTP HEAD request using cURL?

To make an HTTP HEAD request using cURL, you can use the following syntax:

$ curl -I <URL> 

For example, to make a HEAD request to the Google homepage, you can use the following command:

$ curl -I https://www.google.com 

How to make an HTTP OPTIONS request using cURL?

To make an HTTP OPTIONS request using cURL, you can use the following syntax:

$ curl -X OPTIONS <URL> 

For example, to make an OPTIONS request to the Google homepage, you can use the following command:

$ curl -X OPTIONS https://www.google.com 

How to make an HTTP TRACE request using cURL?

To make an HTTP TRACE request using cURL, you can use the following syntax:

$ curl -X TRACE <URL> 

For example, to make a TRACE request to the Google homepage, you can use the following command:

$ curl -X TRACE https://www.google.com 

Tips for troubleshooting cURL errors?

If you are having trouble with cURL, there are a few things you can do to troubleshoot the issue. First, make sure that cURL is installed correctly and that the phpinfo() function is showing that the cURL extension is enabled. Next, try using the -v option (for verbose) when making a request. 

This will display more information about what cURL is doing and can help you to troubleshoot the issue. Finally, if all else fails, you can try to use a different version of cURL.

A Quick Look:

If you're having trouble using your cURL application, there are some quick troubleshooting options you can try.

1. Check your command syntax and make sure the options are correct.

2. Make sure you've correctly spelled the URL or file name.

3. Verify that your firewall or security software isn't blocking cURL requests.

4. If using proxies, check your proxy settings and make sure they're configured correctly.

5. Try running your cURL command with the -v (verbose) option to see more information about the request.

6. Check the server's response code to see if it's indicating an error.

7. If all else fails, try using a different version of cURL.

Conclusion

Overall, using cURL in PHP is a great way to make HTTP requests. It's quick, easy, and most importantly, it's flexible. Whether you're making a GET request or a POST request, cURL has you covered. With a few simple command-line options, you can even make HTTPS requests. So if you need to make an HTTP request in PHP, cURL is definitely the way to go.