PHP, cURL, and HTTP POST example?

<?php
//
// A very simple PHP example that sends a HTTP POST to a remote site
//

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL,"http://www.example.com/tester.phtml");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
            "postvar1=value1&postvar2=value2&postvar3=value3");

// In real life you should use something like:
// curl_setopt($ch, CURLOPT_POSTFIELDS, 
//          http_build_query(array('postvar1' => 'value1')));

// Receive server response ...
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$server_output = curl_exec($ch);

curl_close ($ch);

// Further processing ...
if ($server_output == "OK") { ... } else { ... }
?>

---

Procedural

// set post fields
$post = [
    'username' => 'user1',
    'password' => 'passuser1',
    'gender'   => 1,
];

$ch = curl_init('http://www.example.com');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);

// execute!
$response = curl_exec($ch);

// close the connection, release resources used
curl_close($ch);

// do anything you want with your response
var_dump($response);

Object oriented

<?php

// mutatis mutandis
namespace MyApp\Http;

class CurlPost
{
    private $url;
    private $options;
           
    /**
     * @param string $url     Request URL
     * @param array  $options cURL options
     */
    public function __construct($url, array $options = [])
    {
        $this->url = $url;
        $this->options = $options;
    }

    /**
     * Get the response
     * @return string
     * @throws \RuntimeException On cURL error
     */
    public function __invoke(array $post)
    {
        $ch = \curl_init($this->url);
        
        foreach ($this->options as $key => $val) {
            \curl_setopt($ch, $key, $val);
        }

        \curl_setopt($ch, \CURLOPT_RETURNTRANSFER, true);
        \curl_setopt($ch, \CURLOPT_POSTFIELDS, $post);

        $response = \curl_exec($ch);
        $error    = \curl_error($ch);
        $errno    = \curl_errno($ch);
        
        if (\is_resource($ch)) {
            \curl_close($ch);
        }

        if (0 !== $errno) {
            throw new \RuntimeException($error, $errno);
        }
        
        return $response;
    }
}

Usage

// create curl object
$curl = new \MyApp\Http\CurlPost('http://www.example.com');

try {
    // execute the request
    echo $curl([
        'username' => 'user1',
        'password' => 'passuser1',
        'gender'   => 1,
    ]);
} catch (\RuntimeException $ex) {
    // catch errors
    die(sprintf('Http error %s with code %d', $ex->getMessage(), $ex->getCode()));
}

Side note here: it would be best to create some kind of interface called AdapterInterface for example with getResponse() method and let the class above implement it. Then you can always swap this implementation with another adapter of your like, without any side effects to your application.

Using HTTPS / encrypting traffic

Usually there's a problem with cURL in PHP under the Windows operating system. While trying to connect to a https protected endpoint, you will get an error telling you that certificate verify failed.

What most people do here is to tell the cURL library to simply ignore certificate errors and continue (curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);). As this will make your code work, you introduce huge security hole and enable malicious users to perform various attacks on your app like Man In The Middle attack or such.

Never, ever do that. Instead, you simply need to modify your php.ini and tell PHP where your CA Certificate file is to let it verify certificates correctly:

; modify the absolute path to the cacert.pem file
curl.cainfo=c:\php\cacert.pem

The latest cacert.pem can be downloaded from the Internet or extracted from your favorite browser. When changing any php.ini related settings remember to restart your webserver.

---

A live example of using php curl_exec to do an HTTP post:

Put this in a file called foobar.php:

<?php
  $ch = curl_init();
  $skipper = "luxury assault recreational vehicle";
  $fields = array( 'penguins'=>$skipper, 'bestpony'=>'rainbowdash');
  $postvars = '';
  foreach($fields as $key=>$value) {
    $postvars .= $key . "=" . $value . "&";
  }
  $url = "http://www.google.com";
  curl_setopt($ch,CURLOPT_URL,$url);
  curl_setopt($ch,CURLOPT_POST, 1);                //0 for a get request
  curl_setopt($ch,CURLOPT_POSTFIELDS,$postvars);
  curl_setopt($ch,CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch,CURLOPT_CONNECTTIMEOUT ,3);
  curl_setopt($ch,CURLOPT_TIMEOUT, 20);
  $response = curl_exec($ch);
  print "curl response is:" . $response;
  curl_close ($ch);
?>

Then run it with the command php foobar.php, it dumps this kind of output to screen:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Title</title>

<meta http-equiv="Pragma" content="no-cache">
<meta http-equiv="Expires" content="0">
<body>
  A mountain of content...
</body>
</html>

So you did a PHP POST to www.google.com and sent it some data.

Had the server been programmed to read in the post variables, it could decide to do something different based upon that.

---

It's can be easily reached with:

<?php

$post = [
    'username' => 'user1',
    'password' => 'passuser1',
    'gender'   => 1,
];
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://www.domain.com');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($post));
$response = curl_exec($ch);
var_export($response);

---

Curl Post + Error Handling + Set Headers [thanks to @mantas-d]:

function curlPost($url, $data=NULL, $headers = NULL) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    if(!empty($data)){
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    }

    if (!empty($headers)) {
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    }

    $response = curl_exec($ch);

    if (curl_error($ch)) {
        trigger_error('Curl Error:' . curl_error($ch));
    }

    curl_close($ch);
    return $response;
}


curlPost('google.com', [
    'username' => 'admin',
    'password' => '12345',
]);

---

1.Step by step

Initialize the cURL session:

$url = "www.domain.com";
$ch = curl_init($url);

If your request has headers like bearer token or defining JSON contents you have to set HTTPHEADER options to cURL:

$token = "generated token code";
curl_setopt(
    $ch, 
    CURLOPT_HTTPHEADER, 
    array(
        'Content-Type: application/json', // for define content type that is json
        'bearer: '.$token, // send token in header request
        'Content-length: 100' // content length for example 100 characters (can add by strlen($fields))
    )
);

If you want to include the header in the output set CURLOPT_HEADER to true:

curl_setopt($ch, CURLOPT_HEADER, false);

Set RETURNTRANSFER option to true to return the transfer as a string instead of outputting it directly:

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

To check the existence of a common name in the SSL peer certificate can be set to 0(to not check the names), 1(not supported in cURL 7.28.1), 2(default value and for production mode):

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);

For posting fields as an array by cURL:

$fields = array(
    "username" => "user1",
    "password" => "passuser1",
    "gender" => 1
);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

Execute cURL and return the string. depending on your resource this returns output like result=OK:

$result = curl_exec($ch);

Close cURL resource, and free up system resources:

curl_close($ch);

2.Use as a class

The whole call_cURL class that can be extended:

class class_name_for_call_cURL {
    protected function getUrl() {
        return "www.domain.com";
    }

    public function call_cURL() {
        $token = "generated token code";

        $fields = array(
            "username" => "user1",
            "password" => "passuser1",
            "gender" => 1
        );

        $url = $this->getUrl();
        $output = $this->_execute($fields, $url, $token);
        
        // if you want to get json data
        // $output = json_decode($output);
            
        if ($output == "OK") {
            return true;
        } else {
             return false;
        }
    }

    private function _execute($postData, $url, $token) {
        // for sending data as json type
        $fields = json_encode($postData);

        $ch = curl_init($url);
        curl_setopt(
            $ch, 
            CURLOPT_HTTPHEADER, 
            array(
                'Content-Type: application/json', // if the content type is json
                'bearer: '.$token // if you need token in header
            )
        );
        curl_setopt($ch, CURLOPT_HEADER, false);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

        $result = curl_exec($ch);
        curl_close($ch);

        return $result;
    }
}

Using the class and call cURL:

$class = new class_name_for_call_cURL();
var_dump($class->call_cURL()); // output is true/false

3.One function

A function for using anywhere that needed:

function get_cURL() {

        $url = "www.domain.com";
        $token = "generated token code";

        $postData = array(
            "username" => "user1",
            "password" => "passuser1",
            "gender" => 1
        );

        // for sending data as json type
        $fields = json_encode($postData);

        $ch = curl_init($url);
        curl_setopt(
            $ch, 
            CURLOPT_HTTPHEADER, 
            array(
                'Content-Type: application/json', // if the content type is json
                'bearer: '.$token // if you need token in header
            )
        );
        curl_setopt($ch, CURLOPT_HEADER, false);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

        $result = curl_exec($ch);
        curl_close($ch);

        return $result;
}

This function is usable just by:

var_dump(get_cURL());

---

I'm surprised nobody suggested file_get_contents:

$url = "http://www.example.com";
$parameters = array('username' => 'user1', 'password' => 'passuser1', 'gender' => '1');
$options = array('http' => array(
    'header'  => 'Content-Type: application/x-www-form-urlencoded\r\n',
    'method'  => 'POST',
    'content' => http_build_query($parameters)
));

$context  = stream_context_create($options);
$result = file_get_contents($url, false, $context);

it's simple, it works; I use it in an environment where I control the code at both ends.

even better, use json_decode (and set up your code to return JSON)

$result = json_decode(file_get_contents($url, false, $context), TRUE);

this approach invokes curl behind the scenes, but you don't jump through as many hoops.

Answer refined from this original answer elsewhere on Stack Overflow: PHP sending variables to file_get_contents()

---

curlPost('google.com', [
    'username' => 'admin',
    'password' => '12345',
]);


function curlPost($url, $data) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    $response = curl_exec($ch);
    $error = curl_error($ch);
    curl_close($ch);
    if ($error !== '') {
        throw new \Exception($error);
    }

    return $response;
}

---

If the form is using redirects, authentication, cookies, SSL (https), or anything else other than a totally open script expecting POST variables, you are going to start gnashing your teeth really quick. Take a look at Snoopy, which does exactly what you have in mind while removing the need to set up a lot of the overhead.

---

A simpler answer IF you are passing information to your own website is to use a SESSION variable. Begin php page with:

session_start();

If at some point there is information you want to generate in PHP and pass to the next page in the session, instead of using a POST variable, assign it to a SESSION variable. Example:

$_SESSION['message']='www.'.$_GET['school'].'.edu was not found.  Please try again.'

Then on the next page you simply reference this SESSION variable. NOTE: after you use it, be sure you destroy it, so it doesn't persist after it is used:

if (isset($_SESSION['message'])) {echo $_SESSION['message']; unset($_SESSION['message']);}

---

Here are some boilerplate code for PHP + curl http://www.webbotsspidersscreenscrapers.com/DSP_download.php

include in these library will simplify development

<?php
# Initialization
include("LIB_http.php");
include("LIB_parse.php");
$product_array=array();
$product_count=0;

# Download the target (store) web page
$target = "http://www.tellmewhenitchanges.com/buyair";
$web_page = http_get($target, "");
    ...
?>

---

Examples of sending form and raw data:

$curlHandler = curl_init();

curl_setopt_array($curlHandler, [
    CURLOPT_URL => 'https://postman-echo.com/post',
    CURLOPT_RETURNTRANSFER => true,

    /**
     * Specify POST method
     */
    CURLOPT_POST => true,

    /**
     * Specify array of form fields
     */
    CURLOPT_POSTFIELDS => [
        'foo' => 'bar',
        'baz' => 'biz',
    ],
]);

$response = curl_exec($curlHandler);

curl_close($curlHandler);

echo($response);

---

If you try to login on site with cookies.

This code:

if ($server_output == "OK") { ... } else { ... }

It May not works if you try to login, because many sites return status 200, but the post is not successful.

The easy way to check if the login post is successful is to check if it setting cookies again. If in output have a Set-Cookies string, this means the posts are not successful and it starts a new session.

Also, the post can be successful, but the status can redirect instead of 200.

To be sure the post is successful try this:

Follow location after the post, so it will go to the page where the post does redirect to:

curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

And than check if new cookies existing in the request:

if (!preg_match('/^Set-Cookie:\s*([^;]*)/mi', $server_output)) 

{echo 'post successful'; }

else { echo 'not successful'; }

---

Easiest is to send data as application/json. This will take an array as input and properly encodes it into a json string:

$data = array(
    'field1' => 'field1value',
    'field2' => 'field2value',
)

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));

curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-Type:application/json',
));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$resultStr = curl_exec($ch);
return json_decode($resultStr, true);

---