If you are receiving errors like:
Warning: mysql_close(): 5 is not a valid MySQL-Link resource
Check that you are calling mysql_error() and mysql_errno() BEFORE you call mysql_close().
mysql_errno
(PHP 4, PHP 5)
mysql_errno — Returns the numerical value of the error message from previous MySQL operation
Suggested alternatives
Use of this extension is discouraged. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include:
Description
$link_identifier
= NULL
] )Returns the error number from the last MySQL function.
Errors coming back from the MySQL database backend no longer issue warnings. Instead, use mysql_errno() to retrieve the error code. Note that this function only returns the error code from the most recently executed MySQL function (not including mysql_error() and mysql_errno()), so if you want to use it, make sure you check the value before calling another MySQL function.
Parameters
-
link_identifier
-
The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect() is assumed. If no such link is found, it will try to create one as if mysql_connect() was called with no arguments. If no connection is found or established, an
E_WARNING
level error is generated.
Return Values
Returns the error number from the last MySQL function, or 0 (zero) if no error occurred.
Examples
Example #1 mysql_errno() example
<?php
$link = mysql_connect("localhost", "mysql_user", "mysql_password");
if (!mysql_select_db("nonexistentdb", $link)) {
echo mysql_errno($link) . ": " . mysql_error($link). "\n";
}
mysql_select_db("kossu", $link);
if (!mysql_query("SELECT * FROM nonexistenttable", $link)) {
echo mysql_errno($link) . ": " . mysql_error($link) . "\n";
}
?>
The above example will output something similar to:
1049: Unknown database 'nonexistentdb' 1146: Table 'kossu.nonexistenttable' doesn't exist
See Also
- mysql_error() - Returns the text of the error message from previous MySQL operation
- » MySQL error codes

Function for creating unique md5 keys in a database. If there are duplets, then a new md5-key will be generated. For your use:
function users_md5create($id){
global $mysql_link;
while ($done==0) {
$md5key = md5(time().($id/2).$loop).md5(time().$id.$loop);
$query = "INSERT INTO users_md5create SET md5key='$md5key', fkey='$id', created=UNIX_TIMESTAMP() ";
$mysql_result = mysql_query($query, $mysql_link);
if(mysql_errno($mysql_link)!=1062) $done=1;
$loop++;
}
return($md5key);
}
Watch out! Although mysql_errno() supposedly returns the error number from the last MySQL function, if you don't specify a link identifier, it assumes the last link *opened*, NOT the last link *used*.
That means you can actually have mysql_errno() blindly ignore the error caused by the last MySQL function if it didn't use the last opened link.
Here's an example:
$link1 = mysql_connect('localhost', 'user1', 'password1');
$link2 = mysql_connect('localhost', 'user2', 'password2');
// do something wrong using the first link
mysql_select_db('nonexistentdb', $link1);
// if you don't specify the link identifier ...
if (mysql_errno()) {
// the error from the last MySQL function is not reported
echo mysql_errno() . ': ' . mysql_error() . "\n";
}
All MySQL ErrorCodes can be found in its' on-line manual.
For lazy one here is the link :
http://dev.mysql.com/doc/refman/5.0/en/error-handling.html
All mysqld error messages are located into the file /usr/local/share/mysql/english/errmsg.txt and listed in numerical order from 999 to 1175. You can change the output language as well, issuing the '-L spanish' option for example. See the manual for more details.