- htmlspecialchars: documentation ( source)
<?php
$_POST = array();
$_POST["orderId"]="9879879879_afadak31";
$_POST["orderAmount"]="190.0";
$_POST["referenceId"]="16242";
$_POST["txStatus"]="SUCCESS";
$_POST["paymentMode"]="NET_BANKING";
$_POST["txMsg"]="OK";
$_POST["txTime"]="2018-02-16 01:30:36";
$orderId = $_POST["orderId"];
$orderAmount = $_POST["orderAmount"];
$referenceId = $_POST["referenceId"];
$txStatus = $_POST["txStatus"];
$paymentMode = $_POST["paymentMode"];
$txMsg = $_POST["txMsg"];
$txTime = $_POST["txTime"];
$data = $orderId.$orderAmount.$referenceId.$txStatus.$paymentMode.$txMsg.$txTime;
echo 'Hello ' . htmlspecialchars($_POST["orderId"]) . '!';
echo $data;