How To POST JSON Data with PHP cURL

Written by Rahul, Updated on March 28, 2019

The PHP cURL is a library used for making HTTP requests. In order to use PHP cURL, you must have installed and enabled libcurl module for PHP on your system. In this tutorial, you will learn how to POST JSON data with PHP cURL requests. Basically, there are 4 steps involved to complete a cURL request using PHP.

curl_init — The first step is to initializes a new session of cURL and return a cURL handle to other functions.
curl_setopt — The second step is to set options for a cURL session handle. All these settings are very well explained at curl_setopt().
curl_exec — In third step it perform a cURL session based on above options set.
curl_close — The last step is to close a cURL session initialize by curl_init() and free all resources. Also deleted the cURL handle.

Let’s use the below sample code to create a POST request with PHP cURL.

<?php
// A sample PHP Script to POST data using cURL
// Data in JSON format

$data = array(
    'username' => 'tecadmin',
    'password' => '012345678'
);

$payload = json_encode($data);

// Prepare new cURL resource
$ch = curl_init('https://api.example.com/api/1.0/user/login');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLINFO_HEADER_OUT, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);

// Set HTTP Header for POST request 
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/json',
    'Content-Length: ' . strlen($payload))
);

// Submit the POST request
$result = curl_exec($ch);

// Close cURL session handle
curl_close($ch);

?>

<?php

// A sample PHP Script to POST data using cURL

// Data in JSON format

$data = array(

'username' => 'tecadmin',

'password' => '012345678'

);

$payload = json_encode($data);

// Prepare new cURL resource

$ch = curl_init('https://api.example.com/api/1.0/user/login');

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

curl_setopt($ch, CURLINFO_HEADER_OUT, true);

curl_setopt($ch, CURLOPT_POST, true);

curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);

// Set HTTP Header for POST request

curl_setopt($ch, CURLOPT_HTTPHEADER, array(

'Content-Type: application/json',

'Content-Length: ' . strlen($payload))

);

// Submit the POST request

$result = curl_exec($ch);

// Close cURL session handle

curl_close($ch);

The main thing is that the request must be a POST request with properly json-encoded data in the body. The headers must properly describe the post body.

Rahul

I, Rahul Kumar am the founder and chief editor of TecAdmin.net. I am a Red Hat Certified Engineer (RHCE) and working as an IT professional since 2009..

10 Comments

ioio Reply
October 30, 2019 at 9:02 am
very helpful,
thank you
David Reply
October 24, 2019 at 4:46 pm
Is there a way to avoid the auto “Content-Type: application/x-www-form-urlencoded
” when using POST, I mean, I’m using the following code:
//—————————————————————————————————-
$ch = curl_init();
if(!empty($gdxParams))
{
$curlUrl=$curlUrl.’?’.$gdxParams;
}
$curlOptions=array();
if($gdxMethod==”POST”)
{
$curlOptions=[
CURLOPT_HTTPHEADER=>[
‘x-api-key: ‘.$gdxApiKey,
‘Authorization: Bearer ‘.$gdxApiKey,
‘Content-Type: application/json’,
],
CURLOPT_URL=>$curlUrl,
CURLOPT_CUSTOMREQUEST=>’POST’,
CURLOPT_POSTFIELDS=>json_encode($gdxArrayParams),
CURLOPT_RETURNTRANSFER=>true,
CURLINFO_HEADER_OUT=>true,
];
}
else//Method GET
{
$curlOptions=[
CURLOPT_HTTPHEADER=>[
‘x-api-key: ‘.$gdxApiKey,
‘Authorization: Bearer ‘.$gdxApiKey,
],
CURLOPT_URL=>$curlUrl,
CURLOPT_CUSTOMREQUEST=>’GET’,
CURLOPT_RETURNTRANSFER=>true,
CURLINFO_HEADER_OUT=>true,
];
}
curl_setopt_array($ch, $curlOptions);
$response = curl_exec($ch);
/*—*/
$arrayInfo=array();
$arrayInfo[‘header_info’]=curl_getinfo($ch, CURLINFO_HEADER_OUT);
$arrayInfo[‘response’]=$response;
var_dump($arrayInfo);
/*—*/
//————————————————————————————————
But the header info always gets set as:
//—————————————————————————————————————
‘header_info’ => string ‘POST /v1/reservations?tripId=XXXXXXXXXXXXXXXXXX&lang=es&verifyDuplicatedReservations=true HTTP/1.1
Host: stage.ws.gdx.travel
Accept: */*
x-api-key: XXXXXXXXXXXXXXXXXXXXXX
Authorization: Bearer XXXXXXXXXXXXXXXXXXXXXX
Content-Type: application/json
Content-Length: 221
Content-Type: application/x-www-form-urlencoded
//——————————————————————————————————
If I remove the CURLOPT_POSTFIELDS option, the headers only gets one “Content-Type” line (application/json, the one that I need)
Any clues?
Luis Reply
October 3, 2019 at 10:12 am
it doesn´t work … boolean false is returned, while it works using Postman client
Gautam Reply
August 17, 2019 at 4:57 am
How to make a get request to the api using cURL
Ihab Reply
July 31, 2019 at 7:21 pm
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
‘Content-Type: application/json’,
‘Content-Length: ‘ . strlen($payload))
);
You are asking for strlen($payload); which is the string-length while $payload is an array, so that gives an error?
Any advise?
- Cotton Reply
  August 9, 2019 at 4:13 am
  IHAB,
  json_encode turns the array into a JSON string, so strlen() will work.
RAFAEL LUCAS TEODORO DIAS Reply
July 29, 2019 at 7:53 am
Thanks a lot
Jeffery Triggs Reply
May 31, 2019 at 6:29 pm
This was very helpful! Thanks for posting!
Dheeraj Reply
May 25, 2019 at 4:36 am
Your all tutorilas are awesome bro. Plese provide some a big project in Core Php or CI .
Richard Reply
December 13, 2018 at 9:41 pm
How about radio buttons or select option?

Rahul

10 Comments

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