Introduction

phpMyAdmin can manage a whole MySQL-server (needs a super-user) but also a single database. To accomplish the latter you'll need a properly set up MySQL-user who can read/write only the desired database. It's up to you to look up the appropriate part in the MySQL manual. Currently phpMyAdmin can:

(*) 

phpMyAdmin can compress (Zip, GZip -RFC 1952- or Bzip2 formats) dumps and CSV exports if you use PHP4 >= 4.0.4 with Zlib support (--with-zlib) and/or Bzip2 support (--with-bz2).

 

Configuration

Warning for Mac users: php seems not to like Mac end of lines character ("\r"). So ensure you choose the option that allows to use the *nix end of line character ("\n") in your text editor before registering a script you have modified.

All configurable data is placed in config.inc.php3.

$cfg['PmaAbsoluteUri'] string

Sets here the complete url (with full path) to your phpMyAdmin version. E.g. http://www.your_web.net/path_to_your_phpMyAdmin_directory/.
Don't forget the slash at the end of your url. The url must contain characters that are valid for a url, and on some servers, the path is case-sensitive.

This setting can be dynamically completed. For example, you can try to use such a kind of code:

$cfg['PmaAbsoluteUri'] = (!empty($HTTPS) ? 'https' : 'http') . '://'
                       . $HTTP_HOST . (!empty($SERVER_PORT) ? ':' . $SERVER_PORT : '')
                       . substr($PHP_SELF, 0, strrpos($PHP_SELF, '/')+1);
 
    or
 
$cfg['PmaAbsoluteUri'] = (!empty($HTTPS) ? 'https' : 'http') . '://'
                       . $SERVER_NAME . (!empty($SERVER_PORT) ? ':' . $SERVER_PORT : '')
                       . substr($SCRIPT_NAME, 0, strrpos($SCRIPT_NAME, '/')+1);
        

$cfg['Servers'] array

Since version 1.4.2, phpMyAdmin supports the administration of multiple MySQL servers. Therefore, a $cfg['Servers']-array has been added which contains the login information for the different servers. The first $cfg['Servers'][$i]['host'] contains the hostname of the first server, the second $cfg['Servers'][$i]['host'] the hostname of the second server, etc. If you have only one server to administer, simply leave free the hostname of the other $cfg['Server']-entries.

$cfg['Servers'][$i]['host'] string

The hostname of your $i-th MySQL-server. E.g. localhost.

$cfg['Servers'][$i]['port'] string

The port-number of your $i-th MySQL-server. Default is 3306 (leave blank).

$cfg['Servers'][$i]['socket'] string

The path to the socket to use. Leave blank for default.
To use the socket feature you must run php 3.0.10 or more.

$cfg['Servers'][$i]['connect_type'] string

What type connection to use with the MySQL server. Your options are 'socket' & 'tcp'. It defaults to 'tcp' as that is nearly guarenteed to be available on all MySQL servers, while sockets are not supported on some platforms.

$cfg['Servers'][$i]['controluser'] string
$cfg['Servers'][$i]['controlpass'] string

When using http or cookie authentication modes (or 'config' authentication mode since phpMyAdmin 2.2.1), you need to supply the details of a MySQL account that has SELECT privilege on the mysql.user (all columns except "Password"), mysql.db (all columns) & mysql.tables_priv (all columns except "Grantor" & "Timestamp") tables. This account is used to check what databases the user will see at login.
Please see the install section on "Using http authentication" for more information.

Note that if you try login to phpMyAdmin with this "controluser", you could get some errors, depending the exact privileges you gave to the "controluser". phpMyAdmin does not support a direct login with the "controluser".

In versions before 2.2.5, those were called "stduser/stdpass".

$cfg['Servers'][$i]['auth_type'] string ['http'|'cookie'|'config']

Whether config or cookie or http authentication should be used for this server.

·         'config' authentication ($auth_type = 'config') is the plain old way: username and password are stored in config.inc.php3.

·         'cookie' authentication mode ($auth_type = 'cookie') as introduced in 2.2.3 allows you to log in as any valid MySQL user with the help of... cookies. Log name and password are stored in cookies during the session and password is deleted when it ends.

·         'http' authentication (was called 'advanced' in older versions) ($auth_type = 'http') as introduced in 1.3.0 allows you to log in as any valid MySQL user via HTTP-Auth.


Please see the install section on "Using authentication modes" for more information.

$cfg['Servers'][$i]['user'] string
$cfg['Servers'][$i]['password'] string

The user/password-pair which phpMyAdmin will use to connect to this MySQL-server. This user/password pair is not needed when http or cookie authentication is used, and should be empty.

$cfg['Servers'][$i]['only_db'] string or array

If set to a(an array of) database name(s), only this(these) database(s) will be shown to the user. Since phpMyAdmin 2.2.1, this/these database(s) name(s) may contain MySQL wilcards characters ("_" and "%"): if you want to use literal instances of these characters, escape them (ie use 'my\_db' and not 'my_db').
This setting is an efficient way to lower the server charge since the latter does not need to send MySQL requests to build the available database list. But it does not replace the privileges rules of the MySQL database server. If set, it just means only these databases will be displayed but not at all other databases can't be used.

$cfg['Servers'][$i]['verbose'] string

Only useful when using phpMyAdmin with multiple server entries. If set, this string will be displayed instead of the hostname in the pulldown menu on the main page. This can be useful if you want to show only certain databases on your system, for example.

$cfg['Servers'][$i]['bookmarkdb'] string
$cfg['Servers'][$i]['bookmarktable'] string

Since release 2.2.0 phpMyAdmin allows to bookmark queries. This can be useful for queries you often run.

To use this functionality you have to:

·         create a table following this scheme:
     CREATE TABLE bookmark (
       id int(11) DEFAULT '0' NOT NULL auto_increment,
       dbase varchar(255) NOT NULL,
       user varchar(255) NOT NULL,
       label varchar(255) NOT NULL,
       query text NOT NULL,
       PRIMARY KEY (id)
     );

·         then complete the two variables $cfg['Servers'][$i]['bookmarkdb'] and $cfg['Servers'][$i]['bookmarktable'] with the database and table names you've choosen so phpMyAdmin will be able to find the bookmarks.


Note that
controluser must have SELECT, INSERT and DELETE privileges on the bookmark table. Here is a query to set up those privileges (using "pma" as the controluser:
GRANT SELECT,INSERT,DELETE ON <bookmarkdb>.<bookmarktable> to 'pma'@localhost;

$cfg['Servers'][$i]['relation'] string

Since release 2.2.4 you can describe, in a special 'relation' table, which field is a key in another table (a foreign key). phpMyAdmin currently uses this to

·         make clickable, when you browse the master table, the data values that point to the foreign table;

·         display in an optional tooltip the "display field" when browsing the master table, if you move the mouse to a column containing a foreign key;

·         display links on the table properties page, to check referential integrity (display missing foreign keys) for each described key;

·         in query-by-example, create automatic joints (see an example in the FAQ, section "Using phpMyAdmin").


The keys can be numeric or character.

To use this functionality you have to:

·         create in the same database a table (for example 'relation') following this scheme:
     CREATE TABLE `relation` (
       `master_table` varchar(32) NOT NULL default '',
       `master_field` varchar(32) NOT NULL default '',
       `foreign_table` varchar(32) NOT NULL default '',
       `foreign_field` varchar(32) NOT NULL default '',
       `foreign_display_field` varchar(32) NOT NULL default '',
       PRIMARY KEY (`master_table`,`master_field`)
     ) TYPE=MyISAM COMMENT='Table Relation';

·         put the relation table name in $cfg['Servers'][$i]['relation']

·         then manually fill the relation table with information about the keys.


If you created a relation table before release 2.3.0, you can upgrade it with those commands, assuming your table name is "relation":
     ALTER TABLE relation CHANGE src_table master_table VARCHAR(32) NOT NULL
     ALTER TABLE relation CHANGE src_column master_field VARCHAR(32) NOT NULL
     ALTER TABLE relation CHANGE dest_table foreign_table VARCHAR(32) NOT NULL
     ALTER TABLE relation CHANGE dest_column foreign_field VARCHAR(32) NOT NULL
     ALTER TABLE `relation` ADD `foreign_display_field` VARCHAR(32) NOT NULL;

$cfg['ServerDefault'] integer

If you have more than one server configured, you can set $cfg['ServerDefault'] to any one of them to autoconnect to that server when phpMyAdmin is started, or set it to 0 to be given a list of servers without logging in.
If you have only one server configured,
$cfg['ServerDefault'] MUST be set to that server.

$cfg['OBGzip'] boolean

Defines whether to use gzip output buffering for increased speed in HTTP transfers.

$cfg['PersistentConnections'] boolean

Whether persistent connections should be used or not (mysql_connect or mysql_pconnect).

$cfg['ExecTimeLimit'] integer [number of seconds]

Set the number of seconds a script is allowed to run. If seconds is set to zero, no time limit is imposed.
This setting is used while importing/exporting dump files but has no effect when PHP is running in safe mode.

$cfg['SkipLockedTables'] boolean

Mark used tables and make it possible to show databases with locked tables (since 3.23.30).

$cfg['ShowSQL'] boolean

Defines whether sql-queries generated by phpMyAdmin should be displayed or not.

$cfg['AllowUserDropDatabase'] boolean

Defines whether normal users (non-administrator) are allowed to delete their own database or not. If set as FALSE, the link "Drop Database" will not be shown, and even a "DROP DATABASE mydatabase" will be rejected. Quite practical for ISP's with many customers.

$cfg['Confirm'] boolean

Whether a warning ("Are your really sure..") should be displayed when you're about to loose data.

$cfg['ShowTooltip'] boolean

Defines whether to display table comment as tooltip in left frame or not.

$cfg['LeftFrameLight'] boolean

Defines whether to use select-based menu and display only the current tables in the left frame (smaller page).

$cfg['ShowMysqlInfo'] boolean
$cfg['ShowMysqlVars'] boolean
$cfg['ShowPhpInfo'] boolean
$cfg['ShowChgPassword'] boolean

Defines whether to display the "MySQL runtime information", "MySQL system variables", "PHP information" and "Change password " links or not for simple users at the starting main (right) frame. This setting does not check MySQL commands entered directly.

Please note that to block the usage of phpinfo() in scripts, you have to put this in your php.ini:
    
disable_functions = phpinfo()

Also note that enabling the "Change password " link has no effect with "config" authentication mode: because of the hard coded password value in the configuration file, end users can't be allowed to change their passwords.

$cfg['LoginCookieRecall'] boolean

Define whether the previous login should be recalled or not in cookie authentication mode.

$cfg['ShowStats'] boolean

Defines whether to display space usage and statistics about databases and tables or not.
Note that statistics requires at least MySQL 3.23.3 and that, at this date, MySQL doesn't return such information for Berkeley DB tables.

$cfg['ShowBlob'] boolean

Defines whether BLOB fields are shown when browsing a table's content or not.

$cfg['NavigationBarIconic'] boolean

Defines whether navigation bar buttons contain text or symbols only.

$cfg['ShowAll'] boolean

Defines whether an user should be displayed a "show all (records)" button in browse mode or not.

$cfg['MaxRows'] integer

Number of rows displayed when browsing a resultset. If the resultset contains more rows, Previous/Next links will be shown.

$cfg['Order'] string [DESC|ASC|SMART]

Defines whether fields are displayed in ascending (ASC) order, in descending (DESC) order or in a "smart" (SMART) order -ie descending order for fields of type TIME, DATE, DATETIME & TIMESTAMP, ascending order else- by default.

$cfg['ProtectBinary'] boolean or string

Defines whether BLOB or BINARY fields are protected from edition when browsing a table's content or not. Valid values are:
-
FALSE to allow edition of all fields;
-
blob to allow edition of all fields except BLOBS;
-
all to disallow edition of all BINARY or BLOB fields.

$cfg['ShowFunctionFields'] boolean

Defines whether MySQL functions fields should be displayed or not in edit/insert mode.

$cfg['ZipDump'] boolean
$cfg['GZipDump'] boolean
$cfg['BZipDump'] boolean

Defines whether to allow the use of zip/gzip/bzip compression when creating a dump file or not.

$cfg['ManualBaseShort'] string

If set to an URL which points to the MySQL documentation (on short pages), appropriate help links are generated.

$cfg['DefaultLang'] string

Defines the default language to use, if not browser-defined or user-defined.
See the select_lang.inc.php3 script to know the valid values for this setting.

$cfg['Lang'] string

Force: always use this language (must be defined in the select_lang.inc.php3 script).

$cfg['LeftWidth'] integer

Left frame width in pixel.

$cfg['LeftBgColor'] string [HTML color]
$cfg['RightBgColor'] string [HTML color]

The background colors (HTML) used for both the frames.

$cfg['LeftPointerColor'] string [HTML color]

The color (HTML) used for the pointer in the left frame (does not work with NS4).

$cfg['Border'] integer

The size of a table's border.

$cfg['ThBgcolor'] string [HTML color]

The color (HTML) used for table headers.

$cfg['BgcolorOne'] string [HTML color]

The color (HTML) #1 for table rows.

$cfg['BgcolorTwo'] string [HTML color]

The color (HTML) #2 for table rows.

$cfg['BrowsePointerColor'] string [HTML color]
$cfg['BrowseMarkerColor'] string [HTML color]

The colors (HTML) uses for the pointer and the marker in browse mode (does not work with NS4).
The former feature highlights the row over which your mouse is passing and the latter lets you visually mark/unmark rows by clicking on them.
You can disable both of these features by emptying the respective directive.

$cfg['TextareaCols'] integer
$cfg['TextareaRows'] integer

Number of columns and rows for the textareas.
This value will be emphasized (*2) for sql query textareas.

$cfg['LimitChars'] integer

Maximal number of Chars showed in a TEXT OR a BLOB field on browse view. Can be turned off by a toggle button on the browse page.

$cfg['ModifyDeleteAtLeft'] boolean
$cfg['ModifyDeleteAtRight'] boolean

Defines the place where modify and delete links would be put when tables contents are displayed (you may have them displayed both at the left and at the right). "Left" and "right" are parsed as "top" and "bottom" with vertical display mode.

$cfg['DefaultDisplay'] string

There are 2 display modes: horizontal and vertical. Define which one is displayed by default.

$cfg['RepeatCells'] integer

Repeat the headers every X cells, or 0 to deactivate.

$cfg['ColumnTypes'] array

All possible types of a MySQL column. In most cases you don't need to edit this.

$cfg['AttributeTypes'] array

Possible attributes for fields. In most cases you don't need to edit this.

$cfg['Functions'] array

A list of functions MySQL supports. In most cases you don't need to edit this.

 


Top  -  Requirements  -  Introduction  -  Installation  -  Configuration  -  FAQ  -  Developers  -  Credits


FAQ - Frequently Asked Questions

Server  -  Configuration  -  Limitations  -  Multi-user  -  Browsers  -  Usage tips  -  Project

[Server]

I'm running php 4+ and my server is crashing each time a specific action is required or phpMyAdmin sends a blank page or a page full of cryptic characters to my browser, what can I do?
There are some known php bugs with output buffering and compression.
Try to set the $cfg['OBGzip'] directive to FALSE in your config.inc.php or .php3 file and the zlib.output_compression directive to Off in your php configuration file.
Furthermore, we know about such problems connected to the release candidates of php 4.2.0 (tested with php 4.2.0 RC1 to RC4) together with MS Internet Explorer. Please upgrade to the release version php 4.2.0.

My Apache server crashes when using phpMyAdmin.
You should first try the latest versions of Apache (and possibly MySQL).
See also the other FAQ entry about php bugs with output buffering.
If your server keeps crashing, please ask for help in the various Apache support groups.

Using phpMyAdmin on IIS, I'm displayed the error message: "The specified CGI application misbehaved by not returning a complete set of HTTP headers...."
You just forgot to read the install.txt file from the php distribution. Have a look at the last message in this bug report from the official php bug database.

Using phpMyAdmin on IIS, I'm facing crashes and/or many error messages with the http or advanced authentication mode.
This is a known problem with the php ISAPI filter: it's not so stable. For some more information and complete testings see the messages posted by André B. aka "djdeluxe76" in this thread from the phpWizard forum.
Please use instead the cookie authentication mode.

I can't use phpMyAdmin on PWS: nothing is displayed!
This seems to be a PWS bug. Filippo Simoncini found a workaroud (at this time there is no better fix): remove or comment the DOCTYPE declarations (3 lines) from the scripts header.inc.php3, index.php3, left.php3 and libraries/common.lib.php3.

How can I GZip or Bzip a dump or a CSV export. It seems to not work?
These features are based on the gzencode() and bzcompress() php functions to be more independent of the platform (Unix/Windows, Safe Mode or not, and so on). So, you must have PHP4 >= 4.0.4 and Zlib/Bzip2 support (--with-zlib and --with-bz2).
We faced php crashes when trying to download a dump with MS Internet Explorer when phpMyAdmin is run with a release candidate of php 4.2.0. In this case you should switch to the release version of php 4.2.0.

I cannot insert a text file in a table, and I get an error about safe mode being in effect.
Your uploaded file is saved by PHP in the "upload dir", as defined in php.ini by the variable upload_tmp_dir (usually the system default is /tmp).
We recommend the following setup for Apache servers running in safe mode, to enable uploads of files while being reasonably secure:

I'm having troubles when uploading files. In general file uploads don't work on my system and uploaded files have a Content-Type: header in the first line.
It's not really phpMyAdmin related but RedHat 7.0. You have a RedHat 7.0 and you updated your php rpm to php-4.0.4pl1-3.i386.rpm, didn't you?
So the problem is that this package has a serious bug that was corrected ages ago in php (2001-01-28: see php's bug tracking system for more details). The problem is that the bugged package is still available though it was corrected (see redhat's bugzilla for more details).
So please download the fixed package (4.0.4pl1-9) and the problem should go away.
And that fixes the \r\n problem with file uploads!

I'm having troubles when uploading files with phpMyAdmin running on a secure server. My browser is Internet Explorer and I'm using the Apache server.
As suggested by "Rob M" in the phpWizard forum, add this line to your httpd.conf:
    SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown
It seems to clear up many problems between IE and SSL.

I get an 'open_basedir restriction' while uploading a file from the query box.
Since version 2.2.4, phpMyAdmin supports servers with open_basedir restrictions. Assuming that the restriction allows you to open files in the current directory ('.'), all you have to do is create a 'tmp' directory under the phpMyAdmin install directory, with permissions 777 and the same owner as the owner of your phpMyAdmin directory. The uploaded files will be moved there, and after execution of your SQL commands, removed.

I have lost my MySQL root password, what can I do?
The MySql manual explains how to reset the permissions.

I get an error 'No SQL query' when trying to execute a bookmark.
If PHP does not have read/write access to its upload_tmp_dir, it cannot access the uploaded query.

I get an error 'No SQL query' when trying to submit a query from the convenient text area.
Check the post_max_size directive from your php configuration file and try to increase it.

I have problems with mysql.user field names.
In older MySQL versions, the User and Password fields were named user and password. Please modify your field names to align with current standards.

I cannot upload big dump files.
The first things to check (or ask your host provider to check) are the values of upload_max_filesize, memory_limit and post_max_size in the php.ini configuration file.
All of these three settings limit the maximum size of data that can be submitted and handled by php.

Does phpMyAdmin support MySQL 4?
MySQL 4 is not yet fully supported by phpMyAdmin.
Because of MySQL 4's backwards compatibility you can use phpMyAdmin for administering MySQL 4 servers, but phpMyAdmin does not yet support its new features. Please notice that in this case it is recommended to use php >= 4.1 since older versions of php are not compatible to MySQL 4.
Furthermore, several users reported problems with phpMyAdmin related to bugs in MySQL 4. MySQL 4 is still an alpha release and should be used for test purposes only!

I'm running MySQL 4.0.1 on a Windows NT machine. Each time I create a table the table name is changed to lowercase.
This seems to be a bug of MySQL 4.0.1 because it also appears when using the MySQL commandline. Currently we only know about its appearance on Windows NT systems, but it is possible that it appears on other systems, too.
If you encounter this bug together with another OS and/or MySQL version or you know how to work around it, please post a message into our bug tracker at SourceForge.

[Configuration]

The error message "Warning: Cannot add header information - headers already sent by ..." is displayed, what's the problem?
Edit your config.inc.php or .php3 file and ensure there is nothing (ie no blank lines, no spaces, no characters...) neither before the <?php tag at the beginning, neither after the ?> tag at the end.

phpMyAdmin can't connect to MySQL. What's wrong?
Either there is an error with your PHP setup or your username/password is wrong. Try to make a small script which uses mysql_connect and see if it works. If it doesn't, it may be you haven't even compiled MySQL support into PHP.

The error message "Warning: MySQL Connection Failed: Can't connect to local MySQL server through socket '/tmp/mysql.sock' (111)...") is displayed. What can I do?

For RedHat users, Harald Legner suggests this on the mailing list:

On my RedHat-Box the socket of mysql is /var/lib/mysql/mysql.sock. In your php.ini you will find a line
    mysql.default_socket = /tmp/mysql.sock
change it to
    mysql.default_socket = /var/lib/mysql/mysql.sock
Then restart apache and it will work.

Here is a fix suggested by Brad Ummer in the phpwizard forum:

Have also a look at the corresponding section of the MySQL documentation.

Nothing is displayed by my browser when I try to run phpMyAdmin, what can I do?
Try to set the $cfg['OBGZip'] directive to FALSE in the phpMyAdmin configuration file. It helps sometime.
Also have a look at your php version number: if it contains "4.0b..." it means you're running a beta version of PHP. That's not a so good idea, please upgrade to a plain revision.

Each time I want to insert or change a record or drop a database or a table, an error 404 (page not found) is displayed or, with http or cookie authentication, I'm asked to login again. What's wrong?
Check the value you set for the $cfg['PmaAbsoluteUri'] directive in the phpMyAdmin configuration file.

[Known limitations]

When using http authentication, an user who logged out can not relog in with the same nick.
This is related to the authentication mechanism (protocol) used by phpMyAdmin. We plan to change it as soon as we may find enough free time to do it, but you can bypass this problem: just close all the opened browser windows and then go back to phpMyAdmin. You should be able to logs in again.

When dumping a large table in compressed mode, I get a memory limit error or a time limit error.
As of version 2.2.4, we build the compressed dump in memory, so large tables dumps may hang. The only alternative we can think about (using system calls to mysqldump then gzip or bzip2) would not be applicable in environments where PHP is in safe mode: access to system programs is is limited by the system administrator, and time limit is enforced.

[Using phpMyAdmin]

I can't insert new rows into a table - MySQL brings up a SQL-error.
Examine the SQL error with care. I've found that many programmers specifying a wrong field-type.
Common errors include:

Also, look at the syntax chapter in the MySQL manual to confirm that your syntax is correct.

When I create a table, I click the Index checkbox for 2 fields and phpMyAdmin generates only one index with those 2 fields.
In phpMyAdmin 2.2.0 and 2.2.1, this is the way to create a multi-fields index. If you want two indexes, create the first one when creating the table, save, then display the table properties and click the Index link to create the other index.

How can I insert a null value into my table?
Since version 2.2.3, you have a checkbox for each field that can be null. Before 2.2.3, you had to enter "null", without the quotes, as the field's value.

How can I backup my database or table?
Click on a database or table name in the left frame, the properties will be displayed. Then go to the Dump section, you can dump the structure, the data, or both. This will generate standard SQL statements that can be used to recreate your database/table.

You will need to choose "Save as file", so that phpMyAdmin can transmit the resulting dump to your station. Depending on your PHP configuration, you will see options to compress the dump. See also the $cfg['ExecTimeLimit'] configuration variable.

For additional help on this subject, look for the word "dump" in this document.

How can I restore (upload) my database or table using a dump?
Click on a database name in the left frame, the properties will be displayed. Then in the "Run SQL query" section, type in your local dump filename, or use the Browse button. Then click Go.

For additional help on this subject, look for the word "upload" in this document.

How can I use the relation table in Query-by-example?
Here is an example with the tables persons, towns and countries. Start by creating this:

     CREATE TABLE countries (
       country_code char(1) NOT NULL default '',
       description varchar(10) NOT NULL default '',
       PRIMARY KEY (country_code)
     ) TYPE=MyISAM;

     INSERT INTO countries VALUES ('C', 'Canada');

     CREATE TABLE persons (
       id tinyint(4) NOT NULL auto_increment,
       person_name varchar(32) NOT NULL default '',
       town_code varchar(5) default '0',
       country_code char(1) NOT NULL default '',
       PRIMARY KEY (id)
     ) TYPE=MyISAM;

     INSERT INTO persons VALUES (11, 'Marc', 'S', '');
     INSERT INTO persons VALUES (15, 'Paul', 'S', 'C');

     CREATE TABLE relation (
       master_table varchar(32) NOT NULL default '',
       master_field varchar(32) NOT NULL default '',
       foreign_table varchar(32) NOT NULL default '',
       foreign_field varchar(32) NOT NULL default '',
       PRIMARY KEY (master_table,master_field)
     ) TYPE=MyISAM;

     INSERT INTO relation VALUES ('persons', 'town_code', 'towns', 'town_code');
     INSERT INTO relation VALUES ('persons', 'country_code', 'countries', 'country_code');

     CREATE TABLE towns (
       town_code varchar(5) NOT NULL default '0',
       description varchar(30) NOT NULL default '',
       PRIMARY KEY (town_code)
     ) TYPE=MyISAM;

     INSERT INTO towns VALUES ('S', 'Sherbrooke');
     INSERT INTO towns VALUES ('M', 'Montréal');

Then test like this: