firefly-iii/app/models/Account.php

<?php


class Account extends Elegant
{

    public static $rules
        = [
            'name'    => 'required|between:1,100',
            'user_id' => 'required|exists:users,id'
        ];

    public function accountType()
    {
        return $this->belongsTo('AccountType');
    }

    public function user()
    {
        return $this->belongsTo('User');
    }

    /**
     * Get an accounts current balance.
     *
     * @param \Carbon\Carbon $date
     *
     * @return float
     */
    public function balance(\Carbon\Carbon $date = null)
    {
        $date = is_null($date) ? new \Carbon\Carbon : $date;

        return $this->transactions()
            ->leftJoin('transaction_journals', 'transaction_journals.id', '=', 'transactions.transaction_journal_id')
            ->where('transaction_journals.date', '<=', $date->format('Y-m-d'))->sum('transactions.amount');
    }

    public function transactions()
    {
        return $this->hasMany('Transaction');
    }

}