- var_dump: documentation ( source)
<?php
$cat = '-1';
$dog = '1';
$otherKey = 'greeting';
$content1 = 'hi mom';
$content2 = 'hi dad';
$someArray = array();
$someArray[$cat][$otherKey][] = $content1;
$someArray[$dog][$otherKey][] = $content1;
var_dump($someArray);