PHP MySQL.php

<?php
// open connection
$con = mysqli_connect('host', 'user', 'pass', 'db');
if (!$con) {
	die('Could not connect: ' . mysqli_error($con));
}

// get post data
$data = json_decode(file_get_contents('php://input'), true);

/*
* SELECT
*/
$stmt = $con->prepare("SELECT * FROM x WHERE x = ? AND y = ? AND z = ? AND a IS NULL LIMIT ?");
// bind params
$stmt->bind_param("sisi", $data["string"], $data["int"], $data["string"], $data["int"]);
// execute
$stmt->execute();

// catch error
printf($stmt->error);

// bind & store results
$stmt->bind_result($vars);
$stmt->store_result();

$resultSet = array(); // init result set array

if ($stmt->num_rows === 1) {  // loop over result, here only 1 row should be given
	while ($stmt->fetch()) {
		$row = array(   // current row as array, set key => value
			"key" => $vars,
			"key" => $vars,
		);
		array_push($resultSet, $row);   // add row to resultset
	}
	echo json_encode($resultSet);    // encode to json
}
else echo "false";   // catch

/*
* Update
*/
$stmt = $con->prepare("UPDATE x SET y = ? WHERE z = ?");
// bind params
echo $stmt->affected_rows;


// close stmt & DB connection
$stmt->close(); 
$con->close();
?>