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    mysql_close

    (PHP 4, PHP 5)

    mysql_close — MySQL 接続を閉じる

    警告

    この拡張モジュールは PHP 5.5.0 で非推奨になり、PHP 7.0.0 で削除されました。 MySQLi あるいは PDO_MySQL を使うべきです。詳細な情報は MySQL: API の選択 を参照ください。 この関数の代替として、これらが使えます。

    説明

    mysql_close(resource $link_identifier = NULL): bool

    mysql_close() は、指定した link_identifier が指す MySQL データベースへの非持続的リンクを閉じます。 link_identifier が指定されない場合、最後に オープンされたリンクが使用されます。

    持続的でない MySQL 接続や結果セットは、PHP スクリプトの実行が終了する時点で自動的に破棄されます。 そのため、オープンした接続をクローズしたり結果セットを開放したりすることは必須ではありませんが、 そうしておくことを推奨します。 その時点ですぐに PHP や MySQL にリソースを返せ、パフォーマンスの向上につながるからです。 関連する除法は リソースの開放を参照ください。

    パラメータ

    link_identifier

    MySQL 接続。指定されない場合、mysql_connect() により直近にオープンされたリンクが指定されたと仮定されます。接続が見つからない、または、確立できない場合、E_WARNING レベルのエラーが生成されます。

    戻り値

    成功した場合に true を、失敗した場合に false を返します。

    例

    例1 mysql_close() の例

    <?php
    $link     = mysql_connect('localhost', 'mysql_user', 'mysql_password');
    if (!    $link) {
    die(    '接続できませんでした: ' . mysql_error());
    }
    echo     '接続に成功しました';
    mysql_close($link);
    ?>

    上の例の出力は以下となります。

    接続に成功しました

    注意

    注意:

    mysql_close() は、mysql_pconnect() により生成された持続的リンクを閉じません。 詳細な情報は、マニュアルの 持続的データベース接続を参照ください。

    参考

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    User Contributed Notes 6 notes

    up
    9
    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....
    up
    -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.
    up
    -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.
    up
    -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.
    up
    -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)
    up
    -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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