The function metaForeignKeys() returns an array of the foreign keys associated with a specific table. If there are no foreign keys then the function returns false.

If specified, only returns foreign keys associated with a table owned by that name. Some drivers discard this parameter

if specified, the table and columns are returned in uppercase. Default is lowercase.

If specified, returns the result in associative mode. If ADODB_FETCH_MODE is already associative, then this parameter is discarded.

The method returns an array of data:

• The main key represents the foreign table that the key associated with.
• The values of the key are either a key⇒value pair, the key being the column name of the source table and the value being the column name of the foreign table if the request is associative, or a numeric key with value being the same data represented as local column + '=' + foreign column.

A table child_table has a foreign key that references parent_table. child_table has 2 columns parent_id and parent_type. These 2 columns reference corresponding columns in parent_table, id and type. metaForignKeys() presents this data in the following way:

[
    ['parent_table'] [
        ['parent_id'] => 'id',
        ['parent_type'] => 'type'
    ]
]

[
    [0] => [
        [0] => 'parent_id=id',
        [1] => 'parent_type=type'
    ]
]

/*
 * Connection to MySql Employees Sample database
*/
$db->setFetchMode(ADODB_FETCH_NUM);
 
$p = $db->metaForeignKeys('dept_emp');
print_r($p);
/*
 * prints
Array
(
    [employees] => Array
        (
            [0] => emp_no=emp_no
        )
 
    [departments] => Array
        (
            [0] => dept_no=dept_no
        )
 
)
*/

$db->setFetchMode(ADODB_FETCH_ASSOC);
 
$p = $db->metaForeignKeys('dept_emp');
print_r($p);
/*
 * prints
Array
(
    [employees] => Array
        (
            [emp_no]=>emp_no
        )
 
    [departments] => Array
        (
            [dept_no]=>dept_no
        )
 
)
*/