ontraport_api_call.php

<?php

$header = [
    'Accept: application/json',
    "Api-Appid:XXX",
    "Api-Key:XXX",
];

$contact = [
    'objectID' => 0,
    'email' => 'luis@genesisdigital.co',
    'firstname' =>  'Luis',
    'home_phone' => '+573113727751'
];

$path = 'http://api.ontraport.com/1/objects/saveorupdate';
$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_URL, $path);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $contact);

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

echo $html;