สอบถามเรื่อง error Fatal error: Uncaught Error: Call to undefined function mysql_connect() ครับ

<?php
	$objConnect = mysql_connect("localhost","root","1234") or die(mysql_error());
	$objDB = mysql_select_db("testdb");
	$strSQL = "SELECT * FROM customer WHERE 1 ORDER BY CustomerID DESC ";
	$objQuery = mysql_query($strSQL) or die (mysql_error());
	$intNumField = mysql_num_fields($objQuery);
	$resultArray = array();
	while($obResult = mysql_fetch_array($objQuery))
	{
		$arrCol = array();
		for($i=0;$i<$intNumField;$i++)
		{
			$arrCol[mysql_field_name($objQuery,$i)] = $obResult[$i];
		}
		array_push($resultArray,$arrCol);
	}
	
	mysql_close($objConnect);
	
	echo json_encode($resultArray);
?>

<?php
	$objConnect = mysqli_connect("localhost","root","1234","testdb");

	$objDB = mysqli_select_db($objConnect,"testdb") or die (mysqli_error());

	$strSQL = "SELECT * FROM customer WHERE 1 ORDER BY CustomerID DESC ";
	$objQuery = mysqli_query($objConnect,$strSQL);
	$intNumField = mysqli_num_fields($objQuery);
	$resultArray = array();
	while($obResult = mysqli_fetch_array($objQuery))
	{
		$arrCol = array();
		for($i=0;$i<$intNumField;$i++)
		{
			$arrCol[mysqli_fetch_field_direct($objQuery,$i)] = $obResult[$i];
		}
		array_push($resultArray,$arrCol);
	}
	
	mysqli_close($objConnect);
	
	echo json_encode($resultArray);
?>