pay_privatbank.php

<?php
$id = 75482;
$password = '3A90E5J0f6OUIfqN1Qu59gYrjDgDblfL';
$card = '4627081718568608';
$ssl_verify = TRUE;

$data = <<<XML
<oper>cmt</oper>
<wait>0</wait>
<test>0</test>
<payment id="test3">
    <prop name="b_card_or_acc" value="$card" />
    <prop name="amt" value="1" />
    <prop name="ccy" value="UAH" />
    <prop name="details" value="test%20merch%20not%20active" />
</payment>
XML;
// normalization
$data = preg_replace('/>\s+</', "><", $data);
$data = trim($data);
$signature = sha1(md5($data . $password));

$data = <<<XML
<request>
<merchant>
    <id>$id</id>
    <signature>$signature</signature>
</merchant>
<data>$data</data>
</request>
XML;

$curl = curl_init("https://api.privatbank.ua/p24api/pay_pb");
if (FALSE == $ssl_verify) {
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, FALSE);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
}
// do not output to stdout
curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($curl, CURLOPT_POST, TRUE);
curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
$response = curl_exec($curl);

if (!$response)
    file_put_contents('php://stderr', curl_error($curl));	
$xml = simplexml_load_string($response);
$error = $xml->xpath('//error');
if ($error) {
    $attributes = $error[0]->attributes();
    file_put_contents('php://stderr', $attributes['message']);
}
else {
    $payment = $xml->xpath('//payment');
    echo json_encode($payment);
}