Undefined array key at curl POST method

[ilqcho]

Hello, I need to do a migration of data by posting it from my tables database to an API. I am trying to use curl for the REST setup. Here is an example of my code:

<?php
    include 'config.php';

	function api($url,$data) {
        //API REST
        $fields_string = http_build_query($data);

        print_r($fields_string);  

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, "http://proyectodata/api/$url.php");
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $fields_string );
        $resp = curl_exec($ch);
        curl_close($ch);
        var_dump($resp).'<br/>';

    }
    //id of the promo
    $promo = 33;
    //number of registers to transfer per load
    $cant = 50; 

    if (isset($_SESSION['indexp'])) {
        for ($i=0;$i<10;$i++) {    
            $ini = intval($_SESSION['indexp']);     

            //registers to process during this load
            $registers = $sql->query("SELECT * FROM beneficios LIMIT $ini,$cant");
            $_SESSION['indexp'] = $ini+$cant;

            //migration info
            echo "<p>ini: $ini / users: $registers->num_rows</p>";   

            $todos = array();
            while ($user = $registers->fetch_object()) {
                //set of general data
                $data = array('id' => $user->id, 'participacion' => $user->participacion, 'beneficio' => $user->beneficio,'fecha' => $user->fecha, 	'promo' => $promo);
                echo $sql->error;

                //added to an array for the data load
                array_push($todos,$data);
            }

            //call to API
            api('bulk',$todos);
        }
    ?>

The $data variable contains the data I need to post to the API but when I check the network ar my programmers tool the API is never called.
When I print_r the variable $fields_strin at my api() function I get the following warning message Warning: Undefined array key "indexp" on line 12.
My config.php file has the database config plus the initialization of the session like this: 

session_start();

$_SESSION['indexp'];

Sorry for the long post and code but I am new at PHP and was given this task with an example function (similar to this one that I edited) to do the migration.

Edited November 10, 2022 by ilqcho
security

[ginerjm]

1 hour ago, ilqcho said:

session_start();

$_SESSION['indexp'];

What is the second line above supposed to be doing for you?  It is not a usable statement.  If you had error checking enabled you would probably get a message.  Add this to the start of your script, right after the session_start:

error_reporting(E_ALL);
ini_set('display_errors', '1');