How To Add Arrays Within Arrays And Then Output Their Values In Index Aswell As Associative Array Format?

I got Mysql Tables:

//Valid list of Mysql Tables.
$tables = array('links','countries');

I got Mysql Table 'Links' Columns:

//Valid list of Mysql Table Columns.
$links_table_columns = array('email','domain','url','anchor','description','keyword');

I got Mysql Table 'Countries' Columns:

//Valid list of Mysql Table Columns.
$countries_table_columns = array('Australia','Canada','UK','USA','New Zealand');

Now, how do I add arrays within an array so by just looking at it you can tell which one is array and which ones are it's sub-arrays ?

I made two attempts: 1.

$tables_and_columns = array('table'=>array('links'),array('links'=>array('column'=>email,'column'=>domain,'column'=>url,'column'=>anchor,'column'=>description,'column'=>keyword)));

$valid_param_keys_and_values = 
array($tables = array('links'), $links_table_columns = array('email','domain','url','anchor','description','keyword'))
$countries_tables = array('countries'), $countries_table_columns = array('Australia','Canada','UK','USA','New Zealand')));

Which one is valid, if any ? 
Or, are there other ways of doing adding arrays within array ?
In short, what are the various valid ways you can add arrays within arrays and what are the various ways to output the array values and the sub-arrays' values both in Index and Associative Array format ?

source https://stackoverflow.com/questions/68595903/how-to-add-arrays-within-arrays-and-then-output-their-values-in-index-aswell-as