fgetcsv というものがあってだな

ltsv.php

<?php

$ret = array();

$file = new SplFileObject('hoge.ltsv');
$file->setFlags(SplFileObject::READ_CSV);
$file->setCsvControl("\t");

foreach ($file as $row) {
    $keys = $values = array();

    foreach ($row as $i) {
        list($key, $value) = explode(':', $i, 2);

        $keys[]   = $key;
        $values[] = $value;
    }

    $ret[] = array_combine($keys, $values);
}

var_dump($ret);