......
$conn_DB=mysql_connect($hst,$usr,$pwd) or die(mysql_error());
mysql_select_db($db) or die(mysql_error());
//*** THIS IS VERY IMPORTANT
mysql_query("SET CHARACTER SET utf8");
mysql_query("SET NAMES 'utf8'");
mysql_query("SET COLLATION_CONNECTION = 'utf8_unicode_ci'");
//****
$query = file_get_contents("php://input");
......