mysql_close

(PHP 4, PHP 5)

mysql_close — Close MySQL connection

Avviso

Questa enstensione deprecata da PHP 5.5.0, e sarà rimossa in futuro. Al suo posto, usare l'estensione MySQLi o PDO_MySQL. Vedere anche la guida MySQL: scelta dell'API e le FAQ relative per ulteriori informazioni. Le alternative a questa funzione includono:

mysqli_close()
PDO: Assign the value of null to the PDO object

Descrizione

mysql_close(resource $link_identifier = NULL): bool

mysql_close() closes the non-persistent connection to the MySQL server that's associated with the specified link identifier. If link_identifier isn't specified, the last opened link is used.

Open non-persistent MySQL connections and result sets are automatically destroyed when a PHP script finishes its execution. So, while explicitly closing open connections and freeing result sets is optional, doing so is recommended. This will immediately return resources to PHP and MySQL, which can improve performance. For related information, see freeing resources

Elenco dei parametri

link_identifier: La connessione MySQL. Se l'identificatore di collegamento non è fornito, si utilizza l'ultimo collegamento aperto da mysql_connect(). Se la connessione non viene trovata o se non può essere creata, viene gererato un errore di livello E_WARNING.

Valori restituiti

Restituisce true in caso di successo, false in caso di fallimento.

Esempi

Example #1 mysql_close() example

<?php
$link = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$link) {
    die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully';
mysql_close($link);
?>

Il precedente esempio visualizzerà:

Connected successfully

Note

Nota:
mysql_close() will not close persistent links created by mysql_pconnect(). For additional details, see the manual page on persistent connections.

Vedere anche:

mysql_connect() - Open a connection to a MySQL Server
mysql_free_result() - Free result memory

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User Contributed Notes 6 notes

down

bbodelcampo at yahoo dot co dot uk ¶

19 years ago


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:



<?php

// 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....

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-4

Anonymous ¶

14 years ago


At least with PHP5.3.2 and Windows connecting by tcp, you should always use this mysql_close() function to close and free up the tcp socket being used by PHP.  Garbage collection after script execution does not close the tcp socket on its own.  The socket would otherwise remain in 'wait' state for approximately 30 seconds, and any additional page loads/connection attempts would only add to the total number of open tcp connections.  This wait time does not appear to be configurable via PHP settings.

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-5

mdes[SPAM]saintes at gmail dot com ¶

14 years ago


i just came over a problem that i had with apache.

It crashs and said :

"Parent: child process exited with status 3221225477 -- Restarting."

the error came from the extesion php_mysql.dll

i didn't understand what was the reason of that crash..

Then, i debug the script that i had downloaded and i noticed that that was the function mysql_close() which caused the problem.

The solution is, to send to it the link identifier which is optionnal in the description but cause a crash with no commentary.

Thanks to agneady.

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-5

beer_nomaed _AT_ hotmail _DOT_ com ¶

20 years ago


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.

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-7

omega99999 at gmail dot com ¶

13 years ago


The variable is definitely not optional in 5.3... Caused me a bit of a headache when I was debugging until I realized it was the close function that was causing a hang. So if using just:

<?php
mysql_connect(<...>);

mysql_close();
?>

Use:

<?php
$connection = mysql_connect(<...>);

mysql_close($connection);
?>

(where $connection is any variable of your choice)

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-8

levi at alliancesoftware dot com dot au ¶

19 years ago


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:



<?php

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"

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