PHP: mysql_close

Описание

bool mysql_close ( [resource link_identifier] )

Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.

mysql_close() закрывает соедиение с базой данных MySQL, на которое указывает переданный указатель. Если параметр link_identifier не указан, закрывается последнее открытое (текущее) соединение.

Использование mysql_close() не необходимо для непостоянных соединений. Они автоматически закрываются в конце скрипта. См. также высвобождение ресурсов.

Замечание: mysql_close() не может закрывать постоянные соединения, открытые функцией mysql_pconnect().

Пример 1. Пример использования

<?php $link = mysql_connect("localhost", "mysql_user", "mysql_password") or die("Could not connect: " . mysql_error()); print ("Connected successfully"); mysql_close($link); ?>

См. также mysql_connect() и mysql_pconnect().

mysql_close

bbodelcampo at yahoo dot co dot uk
13-Dec-2005 05:20


A little note about multiple simultaneous connections to different hosts...



I work on a site that pulls content primarily from one db but uses a db on a foreign server to verify licensing.  One might expect the following to work:



// Open the connection to the primary db

$res1 = mysql_connect($host1, $user1, $pass1);

mysql_select_db($db1);



// Open connection to the license server

$res2 = mysql_connect($host2, $user2, $pass2);

mysql_select_db($db2, $res2);



// Pull license data and close when done

mysql_query($check_sql, $res2);

...

mysql_close($res2);



// Now pull content from the primary db

// Not specifying the resource should default to the last open db

mysql_query($query); 

...



Turns out this last query, since it cant find an active connection, will try to connect with mysql_connect() with no paramaters.  But if instead you do it as mysql_query($query, $res1), or alternatively, run the mysql_connect for this host again then it works fine.  Thus, it doesnt seem to be possible to have code with an overarching "global" db connection interspersed with temporary connections to another host/db....

4dacres at gmail dot com
12-Oct-2005 02:23


Read http://bugs.php.net/bug.php?id=30525, and wow... It might be 'just how it works', but this reads like a broken implementation. cameron2 has it right, with this implementation cleaning up connections with mysql_close() can never be done, esp. if the connection is passed to a routine that you have no visibilty into.  You just never know if setting the variable to null or calling mysql_close() is going to error the script.

levi at alliancesoftware dot com dot au
29-Apr-2005 12:03


As at 5.0.x and 4.3.x: This function should never be used with shared links; instead you should set your link variables to null.

(This explains red's and beer's () problems in previous comments)



  Here is how shared links work:

  - Each link is a resource. mysql_connect() by default looks for a resource with the same paramaters. If one exists, it will return the existing resource. 

  - Every assignment of that resource to a variable increases the resource's reference count.

  - When the reference is decremented to zero, the underlying TCP/socket connection is closed.

    - Every assignment of a variable away from that resource decrements the reference count. (This includes a function level variable going out of scope)

    - mysql_close() also decrements the reference count.



Note the last two points: mysql_close() _and_ reassignment of a variable decrement the link's reference count.



A common mistake is a function like:

<?

function dothings() {

  $link = mysql_open(...);

  .. do some queries ..

  mysql_close($link)

  $link = null;

}

?>

this will decrement the counter twice, possibly closing the underlying connection and causing errors in other parts of the program.



http://bugs.php.net/bug.php?id=30525 "this is not a bug but just how it works"

beer_nomaed _AT_ hotmail _DOT_ com
03-Dec-2004 01:26


Be careful when using multiple links to connect to same database (with same username). Unless you specify explicitly in mysql_connect() to create a new link, it will return an already open link. If that would be closed by mysql_close(), it will also (obviously) close the other connection, since the link is the same.

Had lot of trouble figuring it out, since in <=4.3.6 there was a bug which didn't close the connection, but after the patch to >=4.3.7, all my application broke down because of a single script that did this.