คำสั่ง PHP, MySQLที่ใช้แสดงรายชื่อฐานข้อมูล show database ทั้งหมดคือคำสั่งอะไร

<?
$objConnect = mysql_connect("localhost","root","root") or die("Error Connect to Database");
$objQuery = mysql_query("show databases;");
while($objResult = mysql_fetch_array($objQuery))
{
		echo $objResult["Database"]."<br>";
}
mysql_close($objConnect);
?>

<?php
$dbname = 'mydatabase';

if (!mysql_connect('localhost', 'root', 'root')) {
    echo 'Could not connect to mysql';
    exit;
}

$sql = "SHOW TABLES FROM $dbname";
$result = mysql_query($sql);

if (!$result) {
    echo "DB Error, could not list tables<br>";
    echo 'MySQL Error: ' . mysql_error();
    exit;
}

while ($row = mysql_fetch_row($result)) {
    echo "Table: {$row[0]}<br>";
}

mysql_free_result($result);
?>