What am I doing wrong with this curl request in PHP?

Question

I'm trying to write a sample curl request into PHP

POST https://a.klaviyo.com/api/v1/list/{{ LIST_ID }}/members
curl https://a.klaviyo.com/api/v1/list/dqQnNW/members \
  -X POST \
  -d api_key=API_KEY \
  -d email=george.washington@example.com \
  -d properties='{ "$first_name" : "George", "Birthday" : "02/22/1732" }' \
  -d confirm_optin=true

This is my code that I wrote. The part that I'm not getting is how to input the email as data.

$data_string = 
            '{
            "email": "'.$email.'"
            }';



        $ch = curl_init("https://a.klaviyo.com/api/v1/list/$form_id/members?api_key=$mail_api_key");

        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");                                                                     
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);                                                                  
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);                                                                      
        curl_setopt($ch, CURLOPT_HTTPHEADER, array(                                                                          
            'Content-Type: application/json'
            )                                                                       
        );            

The error I'm getting is

Array
(
    [status] => 400
    [message] => This request is missing the following required params: "email".
)

Answer 1

<?php
$email='test@gmmail.com';
$data_string =json_encode($email);


$form_id=5;
$mail_api_key=10;

$ch = curl_init("https://a.klaviyo.com/api/v1/list/$form_id/members?api_key=$mail_api_key");

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Content-Type: application/json'
    )

);

The form_id and api_key i set them hardcoded so i can see the response. This code will work fine for you just remove the $form_id and mail_api_key and set them like you set them first place.

Answer 2

From the php doc: "This parameter can either be passed as a urlencoded string like 'para1=val1&para2=val2&...' or as an array with the field name as key and field data as value." So you should change your json string to an array or urlencode your data.