mysql_close(): 5 is not a valid MySQL-Link resource in C:\wamp\www\Includes\footer.php on line 4

问题

Everyth worked fine, it just decided to stop working and it ruined my whole project and Im at standstill.

This is error:

mysql_close(): 5 is not a valid MySQL-Link resource in C:\wamp\www\Includes\footer.php on line 4

This is footer.php

<?php
//close connection
if (isset($dbh)); {
    mysql_close($dbh);
}
?>

This is connect.php

//set constants
require("quick.php");

//database connection
$dbh = mysql_connect(DB_SERVER, DB_USER, DB_PASS);
if (!$dbh) {  //check connection
        die("Cannot conect! to database ");
    }   

//selecting database
$db_select = mysql_select_db(DB_NAME, $dbh);
if (!$db_select) { //check connection
        die("Cannot connect to database ");
    }
?>

Basically whenever I try to quit mysql this error shows. And it all worked fine not long ago.

回答1:

Somewhere, within your page, there is an assignment that puts $dbh = 5; that overrides your database connection. That is the cause for the error. Search for any assignments to that variable between your database opening and your footer, and you've found your problem.

Note: I wouldn't be that worried about the connection being open as some other commenters here, since if it's not a persistant connection, it will anyway be closed at the end of the script, so I don't see how that would be ruining your whole project. Your code tries to close it at the footer which is not much different than letting it close itself. From the manual:

Using mysql_close() isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution. See also freeing resources.

回答2:

Try this instead:

if (isset($dbh) && is_resource($dbh)) {
    mysql_close($dbh);
} else {
    mysql_close();
}

From manual:

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.

Maybe he's having few connections.. Who knows..

回答3:

All the mysql_* functions will assume "the last connection you opened" if you don't specify a connection. This is useful because you don't have to keep track of it like you do for other libraries. Most likely here you are overwriting the variable $dbh somewhere. Personally I'd use a variable like $_connection if I use one at all.

So just mysql_close() will be enough to close the connection. You need only worry about this kind of thing if you are handling more than one connection at a time.

来源：https://stackoverflow.com/questions/13054044/mysql-close-5-is-not-a-valid-mysql-link-resource-in-c-wamp-www-includes-foot

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