mysql_client_encoding
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....
mysql_close
(PHP 4, PHP 5)
mysql_close — MySQL 接続を閉じる
説明
bool mysql_close
([ resource $link_identifier
] )
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。
持続的でないリンクはスクリプトの実行終了時に自動的に閉じられるの で、通常は mysql_close() を使用する必要はありません。 リソースの解放 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。そのようなリンクがない場合、引数を指定せずに mysql_connect() がコールした時と同様にリンクを確立します。 リンクが見付からない、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。
返り値
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。
add a note
User Contributed Notesmysql_close
bbodelcampo at yahoo dot co dot uk
13-Dec-2005 10:20
13-Dec-2005 10:20
levi at alliancesoftware dot com dot au
29-Apr-2005 04:03
29-Apr-2005 04:03
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:
<?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"
beer_nomaed _AT_ hotmail _DOT_ com
03-Dec-2004 06:26
03-Dec-2004 06:26
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.