<?php

$cont = file_get_contents('catz.txt');
$cont = explode("\n", $cont);
$cats = array();

foreach ($cont as $line)
{
    $temp = explode(":", $line);
    $maincat = $temp[0];

    $temp2 = explode(" => ", $temp[1]);
    $subcat = $temp2[0];
    $catid = $temp2[1];

    $cats[$maincat] = array();
}

foreach ($cont as $line)
{
    $temp = explode(":", $line);
    $maincat = $temp[0];

    $temp2 = explode(" => ", $temp[1]);
    $subcat = $temp2[0];
    $catid = $temp2[1];

    $cats[$maincat][$subcat] = $catid;
}

print_r($cats);

?>