Drupal 6 site-install does not write db-prefix to configuration

I've been thinking about this over the holiday weekend...

var_export would be fine in this instance.

$db_prefix_config = '$db_prefix = ' . var_export($db_prefix, TRUE) . ";\n";

The question, which makes this a little trickier: how to get the pairs?

runserver in Drush 5 doesn't parse arrays from the command line, but I think that in this instance we can get away with it due to the simplicity of database table naming conventions. (Ref: http://dev.mysql.com/doc/refman/5.5/en/identifiers.html and function db_prefix_tables - http://api.drupal.org/api/drupal/includes--database.inc/function/db_pref... )

Here's a $db_prefix definition for a multi-site configuration:

$db_prefix = array(
  'default' => 'default_',
  'users' => 'shared_',
  'sessions' => 'shared_',
  'role' => 'shared_',
  'authmap' => 'shared_',
);

This can be serialized and be included on the command line, but it's a little messy and needs to be generated.

a:5:{s:7:"default";s:8:"default_";s:5:"users";s:7:"shared_";s:8:"sessions";s:7:"shared_";s:4:"role";s:7:"shared_";s:7:"authmap";s:7:"shared_";}

Human readable proposal - If $db_spec['db_prefix'] contains comma (an illegal character for a table name), explode on comma, explode each on colon and build the $db_prefix that way.

A different separator, like | could be used instead of a comma.

Syntax: No spaces, comma separated TABLE:PREFIX

# comma
--db-prefix='default:default_,users:shared_,sessions:shared_,role:shared_,authmap:shared_'
# pipe
--db-prefix='default:default_|users:shared_|sessions:shared_|role:shared_,authmap:shared_'
# serialized, for comparison
--db-prefix='a:5:{s:7:"default";s:8:"default_";s:5:"users";s:7:"shared_";s:8:"sessions";s:7:"shared_";s:4:"role";s:7:"shared_";s:7:"authmap";s:7:"shared_";}'

Code that parses human readable pairs:

// db_prefix - parse multiple table / prefix pairs
if ((FALSE !== strpos($db_spec['db_prefix'], ',')) && FALSE !== strpos($db_spec['db_prefix'], ':')) {
  $db_config_parsed = array();
  $db_config_pairs = explode(',', $db_spec['db_prefix']);
  foreach ($db_config_pairs as $config_pair) {
    $table_prefix = explode(':', $config_pair);
    $db_config_parsed[$table_prefix[0]] = $table_prefix[1];
  }
  // Write db_prefix configuration as an array
  $db_prefix_config = '$db_prefix = ' . var_export($db_config_parsed, TRUE) . ";\n";
  file_put_contents($settingsfile, "\n" . $db_prefix_config, FILE_APPEND);
} else {
  // Write db_prefix configuration as a string
  file_put_contents($settingsfile, "\n" . '$db_prefix = \'' . $db_spec['db_prefix'] . "';\n", FILE_APPEND);
}

Thoughts? Should it include error checking? If it sounds good, I'll write the patch.

Makes sense, thanks for your feedback. I've attached the patch for the 7.x-4.x branch, includes documentation and example.

Sorry about the confusion regarding branches; this patch is against the master. I adjusted the patch to use $command_specific, fixed the coding standard issue, and adjusted the help to reflect that it works for both Drupal 6 and 7 (tested, verified in both configuration and in database).

No modifications were necessary for it to work in Drupal 7, but there is a minor warning from drupal_strlen from the form validation.

Starting Drupal installation. This takes a few seconds ... [0.13 sec, 9.8 B] [ok]
WD php: Warning: mb_strlen() expects parameter 1 to be string, array given in drupal_strlen() (line 441 of /XXX/includes/unicode.inc). [0.28 sec, 17.31 MB] [warning]
WD system: user module installed. [3.28 sec, 18.75 MB] [info]
...
WD cron: Cron run completed. [31.43 sec, 35.01 MB] [notice]
Installation complete.  User name: USERNAME  User password: PASSWORD [31.44 sec, 35 MB] [ok]
mb_strlen() expects parameter 1 to be string, array given in drupal_strlen() (line 441 of /XXX/includes/unicode.inc). [31.44 sec, 35 MB] [warning]
Command dispatch complete [31.44 sec, 34.97 MB] [notice]

Drupal 7 result:

$databases = array (
  'default' =>
  array (
    'default' =>
    array (
      'database' => 'DATABASE',
      'username' => 'USERNAME',
      'password' => 'PASSWORD',
      'host' => 'HOST',
      'port' => '',
      'driver' => 'mysql',
      'prefix' =>
      array (
        'default' => 'default_',
        'users' => 'shared_',
        'sessions' => 'shared_',
        'role' => 'shared_',
        'authmap' => 'shared_',
      ),
    ),
  ),
);