RE: [PHP] Database Class Help

[Ahmed Saad]

On 12/1/05, Albert [EMAIL PROTECTED] wrote:
 The downside of this is that you do not have persistent connections which
 last beyond the end of the script.

Maybe it's not a real downside :)
http://wordpress.org/support/topic/42389
and
http://www.mysql.com/news-and-events/newsletter/2002-11/a86.html

-ahmed

Re: [PHP] Database Class Help

[Unknown Unknown]

Echo should be echo and also are you sure that you have those tables and
databases?? make some DB's called table1 and table 2 and in that make tables
db1 and db2 that might work...

On 12/1/05, Ahmed Saad [EMAIL PROTECTED] wrote:

 On 12/1/05, Albert [EMAIL PROTECTED] wrote:
  The downside of this is that you do not have persistent connections
 which
  last beyond the end of the script.

 Maybe it's not a real downside :)
 http://wordpress.org/support/topic/42389
 and
 http://www.mysql.com/news-and-events/newsletter/2002-11/a86.html

 -ahmed




--
Hi Everyone, I am running PHP 5 on Windosws XP SP2 with MySQL5, Bye Now!

[PHP] Database Class Help

[Ian Barnes]

Hi,

We have a database class that we want to use to connect to multiple
databases at the same time using different variables.

Here is part of the db class:

class db {
  var $dbh = ;
  var $q   = ;

  function db($db_host, $db_user, $db_pass, $db_name) {
$this-dbh = @mysql_pconnect($db_host, $db_user, $db_pass);
$this-select_db($db_name);
  }

  function select_db($db) {
if ([EMAIL PROTECTED]($db, $this-dbh)) {
  die(emCannot select database because:/em/p\npcode .
mysql_error() . /code);
}
  }

  function num_rows($_q) {
if (!$this-q = mysql_query($_q, $this-dbh)) {
  die(Invalid query \code . $_q . /code\/p\npcode .
mysql_error() . /code);
} else {
  return mysql_num_rows($this-q);
}
@mysql_free_result($this-q);
  }
}

In my php file I say something like

?php

Include ( 'db.php' );
$db_1 = new db('server','username','password','db1');
$db_2 = new db('server','username','password','db2');

Echo $db_1-num_rows('select * from table1');
Echo $db_2-num_rows('select * from table2');

?


Now that happens is when I try and do the query for db1, I get told that
db2.table1 doesn't exist. I can swop anything around and it doesn't seem to
work for one of the classes.

Does anyone have any idea as to why this is happening?

Thanks a lot,
Ian

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RE: [PHP] Database Class Help

[Albert]

Ian Barnes wrote:
 We have a database class that we want to use to connect to multiple
 databases at the same time using different variables.


  function db($db_host, $db_user, $db_pass, $db_name) {
$this-dbh = @mysql_pconnect($db_host, $db_user, $db_pass);
$this-select_db($db_name);
  }

 Now that happens is when I try and do the query for db1, I get told that
 db2.table1 doesn't exist. I can swop anything around and it doesn't seem 
 to work for one of the classes.

 Does anyone have any idea as to why this is happening?

You didn't specify but I guess all your databases are on the same server.

When accessing multiple databases on the same server using multiple
instances of a class, you need to make multiple connections to the server.

By default PHP creates only ONE connection to a server and the database you
select is linked to the connection. So instantiating another instance will
use the previous established connection and change the database.

To force a new connection, you need to use mysql_connect() instead of
mysql_pconnect(). When using mysql_connect() you can specify:

$this-dbh = @mysql_connect($db_host, $db_user, $db_pass, true);

[quote from=PHP manual]
resource mysql_connect ( [string server [, string username [, string
password [, bool new_link [, int client_flags ] )
[/quote]

Which will force a new connection. By default PHP will use a connection
which have already been established.

Take care when doing this as each time you instantiate a class a new
connection to the database will be created adding additional load on your
database which can cause a denial of service.

I normally store a list of connections to servers and databases in a
variable which can be accessed by the script. Every time I instantiate a new
instance of my database class I first make sure that a connection to that
server and database does not already exist. If it does exist then I call
mysql_connect() without the true for new_link otherwise I call
mysql_connect() with the true for new_link.

The downside of this is that you do not have persistent connections which
last beyond the end of the script.

Hope it helps

Albert



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