Here’s a very simple PHP sample to SEARCH for an existing lead:

<?php

$ch = curl_init();
// CONNECT TO API, VERIFY MY API KEY AND PASSWORD AND GET THE LEAD DATA
curl_setopt($ch, CURLOPT_URL,"https://app.kartra.com/api");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
    http_build_query(
        array(
            'app_id' => 'AIm863DwsOW',
            'api_key' => 'QG9GPLW8G',
            'api_password' => 'kdwFAfwrfVS',
            'lead' => array(
                'id' => '3232323223', //you may pass either ID or EMAIL. If both, the system will pick ID
                'email' => '[email protected]',     
            ),
            'actions' => array(
                '0' => array(
                       'cmd' => 'search_lead',
                 ),
            )
      )
   )
);

// REQUEST CONFIRMATION MESSAGE FROM API…
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$server_output = curl_exec ($ch);
curl_close ($ch);
$server_json = json_decode($server_output);
switch ($server_json->status) {
    case "Error" :
        // process what error was about
        break;
    case "Success" :
        // after this you can use the info passed from kartra in your own scripts. 
        // Ex: $server_json->lead_details contains the lead details.
        break;
}

?>