<?php
$var = array(
    '*original' => array(
        'id' => 1,
        'user_id' => 3,
        'reference' => 'c8d2076672c9631e8c048589f3a9a26f3961',
        'status' => 'Pendente',
        'paymentMethod' => "ph",
        'date' => "2018-08-30",
        'paymentLink' => "",
        'created_at' => "2018-08-30 17:41:39",
        'updated_at' => "0000-00-00 00:00:00",
        'pacote' => 1,
        'tipo' => "Ativação de pacote",
        'valor' => 0,
        'transaction_id' => NULL,
    )
);


$recuperado = $var["*original"]["transaction_id"];

var_dump($recuperado);