<?php

$tiger = array ("orange", "white");
$cat = array ("black", "white", "brown");
$fruit = array ("purple", "red", "green", "brown");

$arrays = compact('tiger', 'cat', 'fruit');
$values = array_unique(call_user_func_array('array_merge_recursive', $arrays));

foreach ($values as $value) {
    $found = array();
    foreach ($arrays as $name => $bag) {
        if (in_array($value, $bag)) {
            $found[] = $name;
        }
    }
    echo "$value: ".implode(", ", $found)."\n";
}