Since Version 4.1 (or 5?) of MySQL you can comment each field of a table. Here is an example how to get these field-comments in PHP:

// Name of Table
$myTab = 'myTable';

// Resultarray (Fieldname => Comment)
$fieldComments = array(); 

// Get the Values
$tabFields = mysql_query('SHOW FULL COLUMNS
                          FROM `'.$myTab.'`');
while ($fieldAtts = mysql_fetch_assoc($tabFields)){
    if (! empty($fieldAtts['Comment'])){
        $fieldComments[$fieldAtts['Field']]
          = $fieldAtts['Comment'];
    }
}

// Example: Output to Browser
echo '<pre>'.print_r ($fieldComments, true).'</pre>';