What is cURL in PHP?

Question

cURL is a library that lets you make HTTP requests in PHP. Everything you need to know about it (and most other extensions) can be found in the PHP manual.

In order to use PHP's cURL functions you need to install the » libcurl package. PHP requires that you use libcurl 7.0.2-beta or higher. In PHP 4.2.3, you will need libcurl version 7.9.0 or higher. From PHP 4.3.0, you will need a libcurl version that's 7.9.8 or higher. PHP 5.0.0 requires a libcurl version 7.10.5 or greater.

You can make HTTP requests without cURL, too, though it requires allow_url_fopen to be enabled in your php.ini file.

// Make a HTTP GET request and print it (requires allow_url_fopen to be enabled)
print file_get_contents('http://www.example.com/');

cURL is a way you can hit a URL from your code to get a html response from it. cURL means client URL which allows you to connect with other URLs and use their responses in your code.

CURL in PHP:

Summary:

The curl_exec command in PHP is a bridge to use curl from console. curl_exec makes it easy to quickly and easily do GET/POST requests, receive responses from other servers like JSON and download files.

Warning, Danger:

curl is evil and dangerous if used improperly because it is all about getting data from out there in the internet. Someone can get between your curl and the other server and inject a rm -rf / into your response, and then why am I dropped to a console and ls -l doesn't even work anymore? Because you mis underestimated the dangerous power of curl. Don't trust anything that comes back from curl to be safe, even if you are talking to your own servers. You could be pulling back malware to relieve fools of their wealth.

Examples:

These were done on Ubuntu 12.10

1. Basic curl from the commandline:

   el@apollo:/home/el$ curl http://i.imgur.com/4rBHtSm.gif > mycat.gif
     % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                    Dload  Upload   Total   Spent    Left  Speed
   100  492k  100  492k    0     0  1077k      0 --:--:-- --:--:-- --:--:-- 1240k
   

   Then you can open up your gif in firefox:

   firefox mycat.gif
   

   Glorious cats evolving Toxoplasma gondii to cause women to keep cats around and men likewise to keep the women around.

2. cURL example get request to hit google.com, echo to the commandline:

   This is done through the phpsh terminal:

   php> $ch = curl_init();
   
   php> curl_setopt($ch, CURLOPT_URL, 'http://www.google.com');
   
   php> curl_exec($ch);
   

   Which prints and dumps a mess of condensed html and javascript (from google) to the console.

3. cURL example put the response text into a variable:

   This is done through the phpsh terminal:

   php> $ch = curl_init();
   
   php> curl_setopt($ch, CURLOPT_URL, 'http://i.imgur.com/wtQ6yZR.gif');
   
   php> curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
   
   php> $contents = curl_exec($ch);
   
   php> echo $contents;
   

   The variable now contains the binary which is an animated gif of a cat, possibilities are infinite.

4. Do a curl from within a PHP file:

   Put this code in a file called myphp.php:

   <?php
     $curl_handle=curl_init();
     curl_setopt($curl_handle,CURLOPT_URL,'http://www.google.com');
     curl_setopt($curl_handle,CURLOPT_CONNECTTIMEOUT,2);
     curl_setopt($curl_handle,CURLOPT_RETURNTRANSFER,1);
     $buffer = curl_exec($curl_handle);
     curl_close($curl_handle);
     if (empty($buffer)){
         print "Nothing returned from url.<p>";
     }
     else{
         print $buffer;
     }
   ?>
   

   Then run it via commandline:

   php < myphp.php
   

   You ran myphp.php and executed those commands through the php interpreter and dumped a ton of messy html and javascript to screen.

   You can do GET and POST requests with curl, all you do is specify the parameters as defined here: Using curl to automate HTTP jobs

Reminder of danger:

Be careful dumping curl output around, if any of it gets interpreted and executed, your box is owned and your credit card info will be sold to third parties and you'll get a mysterious $900 charge from an Alabama one-man flooring company that's a front for overseas credit card fraud crime ring.

cURL is a way you can hit a URL from your code to get a HTML response from it. It's used for command line cURL from the PHP language.

<?php
// Step 1
$cSession = curl_init(); 
// Step 2
curl_setopt($cSession,CURLOPT_URL,"http://www.google.com/search?q=curl");
curl_setopt($cSession,CURLOPT_RETURNTRANSFER,true);
curl_setopt($cSession,CURLOPT_HEADER, false); 
// Step 3
$result=curl_exec($cSession);
// Step 4
curl_close($cSession);
// Step 5
echo $result;
?> 

Step 1: Initialize a curl session using curl_init().

Step 2: Set option for CURLOPT_URL. This value is the URL which we are sending the request to. Append a search term curl using parameter q=. Set option for CURLOPT_RETURNTRANSFER. True will tell curl to return the string instead of print it out. Set option for CURLOPT_HEADER, false will tell curl to ignore the header in the return value.

Step 3: Execute the curl session using curl_exec().

Step 4: Close the curl session we have created.

Step 5: Output the return string.

public function curlCall($apiurl, $auth, $rflag)
{
    $ch = curl_init($apiurl);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

    if($auth == 'auth') { 
        curl_setopt($ch, CURLOPT_USERPWD, "passw:passw");
    } else {
        curl_setopt($ch, CURLOPT_USERPWD, "ss:ss1");
    }
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $dt = curl_exec($ch);        
    curl_close($ch);
    if($rflag != 1) {
        $dt = json_decode($dt,true);        
    }
    return $dt;
}

This is also used for authentication. We can also set the username and password for authentication.

For more functionality, see the user manual or the following tutorial:

http://php.net/manual/en/ref.curl.php
http://www.startutorial.com/articles/view/php-curl

Firstly let us understand the concepts of curl, libcurl and PHP/cURL.

1. curl: A command line tool for getting or sending files using URL syntax.

2. libcurl: a library created by Daniel Stenberg, that allows you to connect and communicate to many different types of servers with many different types of protocols. libcurl currently supports the http, https, ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with PHP's ftp extension), HTTP form based upload, proxies, cookies, and user+password authentication.

3. PHP/cURL: The module for PHP that makes it possible for PHP programs to use libcurl.

How to use it:

step1: Initialize a curl session use curl_init().

step2: Set option for CURLOPT_URL. This value is the URL which we are sending the request to.Append a search term "curl" using parameter "q=".Set option CURLOPT_RETURNTRANSFER, true will tell curl to return the string instead ofprint it out. Set option for CURLOPT_HEADER, false will tell curl to ignore the header in the return value.

step3: Execute the curl session using curl_exec().

step4: Close the curl session we have created.

step5: Output the return string.

Make DEMO :

You will need to create two PHP files and place them into a folder that your web server can serve PHP files from. In my case I put them into /var/www/ for simplicity.

1. helloservice.php and 2. demo.php

helloservice.php is very simple and essentially just echoes back any data it gets:

<?php
  // Here is the data we will be sending to the service
  $some_data = array(
    'message' => 'Hello World', 
    'name' => 'Anand'
  );  

  $curl = curl_init();
  // You can also set the URL you want to communicate with by doing this:
  // $curl = curl_init('http://localhost/echoservice');

  // We POST the data
  curl_setopt($curl, CURLOPT_POST, 1);
  // Set the url path we want to call
  curl_setopt($curl, CURLOPT_URL, 'http://localhost/demo.php');  
  // Make it so the data coming back is put into a string
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
  // Insert the data
  curl_setopt($curl, CURLOPT_POSTFIELDS, $some_data);

  // You can also bunch the above commands into an array if you choose using: curl_setopt_array

  // Send the request
  $result = curl_exec($curl);

  // Get some cURL session information back
  $info = curl_getinfo($curl);  
  echo 'content type: ' . $info['content_type'] . '<br />';
  echo 'http code: ' . $info['http_code'] . '<br />';

  // Free up the resources $curl is using
  curl_close($curl);

  echo $result;
?>

2.demo.php page, you can see the result:

<?php 
   print_r($_POST);
   //content type: text/html; charset=UTF-8
   //http code: 200
   //Array ( [message] => Hello World [name] => Anand )
?>

The cURL extension to PHP is designed to allow you to use a variety of web resources from within your PHP script.

cURL in PHP is a bridge to use command line cURL from the php language