Strange behaviour trying to detect errors selecting a database - php

Question

I have the following code in php:
<?php
$con = mysql_connect("localhost","john","john");
mysql_select_db("data", $con);
if (!$mysql_select_db) {
die ('Cannot use data : ' . mysql_error());
}
$result = mysql_query("SELECT * FROM test where huss='hussein'");
while ($row = mysql_fetch_array($result)) {
echo "ADSDAD";
echo "<br />";
}
if (!$con) {
die('ERROR Could not connect: ' . mysql_error());
}
mysql_close($con);
?>
I was able to connect to the MySQL server, but I can't seem to select the relevant database.
Being printed is the hard-coded text Cannot use data :, but no MySQL error message follows it. If the MySQL connection had failed then I would have expected a MySQL error message to appear after the hard-coded text.
What am I doing wrong?

Answer 1

The problem's here:
mysql_select_db("data", $con);
if (!$mysql_select_db) {
die ('Cannot use data : ' . mysql_error());
}
You don't have a variable $mysql_select_db, and it doesn't magically map to the result of the last time you called mysql_select_db.
So, instead:
$result = mysql_select_db("data", $con);
if (!$result) {
die ('Cannot use data : ' . mysql_error());
}
Or:
if (!mysql_select_db("data", $con)) {
die ('Cannot use data : ' . mysql_error());
}