PHP: connected to database, but mysql_query fails - php

Question

I have very strange problem with PHP which I am starting to learn .. I have created tables in MySQL database with some data, and now I want to show them in webpage.
This is my source where I have this problem:
<?php
// Here I open connection
$con = mysql_connect("localhost","root","aaaaaa");
// set the mysql database
$db = mysql_select_db("infs", $con);
// I check the connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
else {
// It always goes here
echo "Connected to database!";
}
// I am testing very simple SQL query.. there should be no problem
$result = mysql_query("SELECT * FROM cathegories", $con, $db);
if (!$result) {
// but it always dies
$message = 'Invalid query: ' . mysql_error() . "\n";
$message .= 'Whole query: ' . $query;
die($message);
}
mysql_close($con);
?>
What is wrong?
Thanks in advance!

Answer 1

You are mixing mysql and mysqli.
Try something like:
<?php
$con= new mysqli("localhost","user","passwd","database");
if ($con->connect_errno){
echo "could not connect";
}
$select = "SELECT * FROM tablename";
if($result = $con->query($select)){
while($row = $result->fetch_object()){
echo $row->rowname."<br>";
}
}
else { echo 'no result'; }
$con->close();
?>

Answer 2

// Here I open connection
$con = mysql_connect("localhost","root","aaaaaa");
// set the mysql database
$db = mysql_select_db("infs", $connection);
change to
// Here I open connection
$con = mysql_connect("localhost","root","aaaaaa");
// set the mysql database
$db = mysql_select_db("infs", $con);

Answer 3

mysql_query only takes two parameters - the actual SQL and then the link identifier (I assume in your case that's stored in $con; therefore remove $db from the third parameter).
You don't even need the second $con parameter really.
Where's the actual logic to connect to the database initially? Just because mysqli_connect_errno() doesn't return an error it doesn't mean the connection actually exists and that $con is available in the current scope.
I'd var_dump($con) before the mysql query to make sure it's a valid connection.