two mysqli connections simultaneously

Question

I tried to alter OOP script presented here:

to handle two databases at once (depending on function needs), but it seems not to work at all. I get an error message: mysqli_query() expects at least 2 parameters, 1 given in ...DAL.php on line 60

private function dbconnect($usedb)
{
    switch($usedb)
    {
        case '':
        echo "Error choosing database to operate on.";
        break;
        case '1':
        $conn = new mysqli(DB1_HOST, DB1_USER, DB1_PASSWORD,DB1_DB) or die ("<br>Could not connect to MySQL server");
        //mysqli_select_db(DB1_DB,$conn) or die ("<br>Could not select the main database.");
        return $conn;
        break;
        case '2':
        $conn = new mysqli(DB2_HOST, DB2_USER, DB2_PASSWORD,DB2_DB) or die ("<br>Could not connect to MySQL server");
        //mysqli_select_db(DB2_DB,$conn) or die ("<br>Could not select the client database.");
        return $conn;
        break;
    }
}

private function query($usedb,$sql)
{
    $this->dbconnect($usedb);  
    $res = mysqli_query($sql);

Can this work eventually? How to handle two databases at once if called from a single function that is making querying much easier? What I do wrong?

What does the error message say? Have you looked at the documentation to see what parameters mysqli_query needs? — andrewsi, May 17 '13 at 14:58
`mysqli_query` first parameter should be a `mysqli` instance. — Henrique Barcelos, May 17 '13 at 14:59
Just add `$usedb` to `mysqli_query` like this, `mysqli_query($userdb, $sql)` — Josh Balcitis, May 17 '13 at 15:00
$sql variable contains the exact sql statement to be processed. This code is based on: http://net.tutsplus.com/tutorials/php/simple-php-class-based-querying/ — jakubplus, May 17 '13 at 16:49
Also, take a look at https://stackoverflow.com/questions/274892/how-do-you-connect-to-multiple-mysql-databases-on-a-single-webpage/45688265#45688265 — Nagibaba, Aug 15 '17 at 07:44

score 1 · Answer 1 · answered May 17 '13 at 14:59

1

This piece of code:

private function query($usedb,$sql)
{
$this->dbconnect($usedb);  
$res = mysqli_query($sql);

Should be like:

private function query($usedb,$sql)
{
$conn = $this->dbconnect($usedb);  
$res = mysqli_query($conn,$sql);

mysqli_close($conn); //dont forget to close it

And in you dbconnect function you should use procedural style:

return $link = mysqli_connect("localhost", "my_user", "my_password", "world");

answered May 17 '13 at 14:59

Hackerman

12,139
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Well, the worst problem is, that even now, I get error like: "mysqli_select_db() expects parameter 1 to be mysqli, string given" How constant, same as first database name, can be a string? Should I convert this to an object? – jakubplus May 17 '13 at 16:47
are you using object style on yur function and procedural style outside....you change your code like the return $link y posted on my answer? – Hackerman May 17 '13 at 16:52
Robert Rozas, you've been almost exact with your answer. This totally works for me: private function query($usedb,$sql) { $conn = $this->dbconnect($usedb); $res = $conn->query($sql); – jakubplus May 18 '13 at 10:27

score 1 · Answer 2 · answered May 17 '13 at 15:00

1

You don't reconnect to the database every time, you save the link. This is one way to do it.

$dbs= array(1=>dbconnect(1), 2=>dbconnect(2));
private function query($usedb,$sql)
{
     global $dbs;
     return mysqli_query($dbs[$usedb], $sql);
}

answered May 17 '13 at 15:00

Adder

5,708
1
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56

score 0 · Answer 3 · answered May 17 '13 at 15:01

When you use it procedurally like that:

$res = mysqli_query($sql);

It expects: (SRC: http://php.net/manual/en/mysqli.query.php)

 mixed mysqli_query ( mysqli $link , string $query [, int $resultmode = MYSQLI_STORE_RESULT ] )

So, you're missing the first parameter.

Since you're returning the object. I would change your private function 'query' to:

$mysql = $this->dbconnect($usedb);
$res = $mysql->query($sql);

two mysqli connections simultaneously

3 Answers3