Log API call inside file

We have this code which calls to an API function, we would like to log all requests to a file (in a secure way). We can handle multiple requests at once. Code works smooth on production environment, we need to log calls to a file to verify which call made which error. $userId = $current_user->ID; $idRichiesta = $[login to view URL](100000,999999); $timestamp = round(microtime(true) * 1000); $terminalid = get_user_meta($userId,'billing_wcj_checkout_field_3'); $codPv = get_user_meta($userId,'billing_wcj_checkout_field_2'); $url = $domain; $piva = get_user_meta($userId,'billing_wcj_checkout_field_1'); $servizio = 'EC'; $request = array('grant_type' => 'client_credentials','client_id' => '**','client_secret' => '**'); $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, "**"); curl_setopt($ch, CURLOPT_POST, TRUE); curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, TRUE); curl_setopt($ch, CURLOPT_VERBOSE, true); curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($request)); curl_setopt($ch, CURLOPT_SSLCERT, $_SERVER['DOCUMENT_ROOT'].'/../../csr/**'); $response = curl_exec($ch); $responseObj = json_decode($response); $accessToken = $responseObj->access_token; $request = array('timestamp'=>$timestamp,'idRichiesta'=>$idRichiesta[0],'terminalid'=>$terminalid[0],'codPv'=>$codPv[0],'url'=>$url,'piva'=>$piva[0],'servizio'=>$servizio); $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, "**"); curl_setopt($ch, CURLOPT_POST, TRUE); curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, TRUE); curl_setopt($ch, CURLOPT_VERBOSE, true); $authorization = "Authorization: Bearer ".$accessToken; curl_setopt($ch, CURLOPT_HTTPHEADER, array($authorization,'Content-Type: application/json')); curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($request)); curl_setopt($ch, CURLOPT_SSLCERT, $_SERVER['DOCUMENT_ROOT'].'/../../csr/**'); $response = curl_exec($ch); $responseObj = json_decode($response); if($responseObj->esito=='OK') { $blog_id = wpmu_create_blog( $domain, $path, $blog_title, $current_user->ID, $meta, get_current_network_id() ); if ( is_wp_error( $blog_id ) ) { return false; } confirm_another_blog_signup( $domain, $path, $blog_title, $current_user->user_login, $current_user->user_email, $meta, $blog_id ); $blogUrl = get_blog_option($blog_id,'siteurl'); $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $blogUrl.'/wp-admin/[login to view URL]'); curl_setopt($ch, CURLOPT_POST, TRUE); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE); curl_setopt($ch, CURLOPT_POSTFIELDS, array('action'=>'latepoint_activate')); curl_exec($ch); $tablePrifix = $wpdb->get_blog_prefix($blog_id); $wpdb->insert($tablePrifix.'latepoint_settings', array("**'))); $wpdb->insert($tablePrifix.'latepoint_settings', array("name"=>"**'))); $wpdb->insert($tablePrifix.'latepoint_settings', array("name"=>"**'))); $wpdb->insert($tablePrifix.'latepoint_settings', array("name"=>"**'))); $wpdb->insert($tablePrifix.'latepoint_settings', array("name"=>"**'))); return true; } else { $errorMsg["1"] = "ERROR 1"; $errorMsg["2"] = "ERROR 2"; $errorMsg["3"] = "ERROR 3"; $errorMsg["4"] = "ERROR 4"; $errorMsg["99"] = "ERROR 99"; $errors->add('error',$errorMsg[abs($responseObj->codiceEsito)]); signup_another_blog( $blogname, $blog_title, $errors ); return false; }