SugarCRM Opportunity before_save hook to create a Contract

<?php
/**
 * Class to assist in creating Contracts from Opportunities given that conditions are met.
 *
 * Conditions are that the Opportunity is being marked as "Closed Won" (i.e. that it is being changed
 * to this status from another status) and that it has a valid value in install_c.
 */
class psi_create_contract{

    /**
     * @var Opportunity object that we get just by being here
     */
    private $bean;

    /**
     * @var Contract object we create later in the script
     */
    private $contract;

    /**
     * @var bool set debug value for this script
     */
    private $debug_to_screen = TRUE;

    /**
     * init/entry point from the Logic Hook, controller method
     */
    public function psi_create_contract($bean,$event,$args){
        $this->bean = $bean;
        $this->debug($this->check_sales_stage(),"BOOL result of check_sales_stage ");
        $this->debug($this->check_install_date(),"BOOL result of check_install_date ");
        if($this->check_sales_stage() && $this->check_install_date()){
            $this->create_contract();
        }
    }

    /**
     * check to see if the sales stage is set to Closed Won, and that this is a change
     * to this value from some other value
     *
     * @returns bool
     */
    private function check_sales_stage(){
        if($this->bean->sales_stage == 'Closed Won' && $this->bean->sales_stage != $this->bean->fetched_row['sales_stage'])
            return true;
        else
            return false;
    }

    /**
     * check to see if the install_date_c is set
     *
     * @returns bool
     */
    private function check_install_date(){
        if(isset($this->bean->install_c) && !empty($this->bean->install_c))
            return true;
        else
            return false;
    }

    /**
     * create the contract using provided information, then set
     * $this->contract with the new object
     */
    private function create_contract(){
        $this->debug($this->bean->install_c, "Passed in date value ");
        $contract = new Contract();
        $contract->name = $this->bean->name . " Contract";
        $contract->start_date = $this->bean->install_c;
        $contract->end_date = $this->add_days_date_string($this->bean->install_c,'+1 Year');
        $contract->opportunity_id = $this->bean->id;
        $contract->opportunity_name = $this->bean->name;
        $contract->account_id = $this->bean->account_id;
        $contract->account_name = $this->bean->account_name;
        $contract->total_contract_value = $this->bean->amount;
        $contract->assigned_user_id = $this->bean->assigned_user_id;
        $contract->assigned_user_name = $this->bean->assigned_user_name;
        $contract->save();
        $this->contract = $contract;
        $this->debug($this->contract,"Newly created contract ",FALSE);
    }

    /**
     * convert a date string of specified format to date object, return same-format
     * string plus added number of days/months/years
     *
     * @param $date_string string of date
     * @param $addendum amount of time/days to add, e.g. +8 months
     * @param $format string date-format
     * @return string of date plus 1 year
     */
    private function add_days_date_string($date_string,$addendum = '+1 Year',$format = "Y-m-d"){
        $do = DateTime::createFromFormat($format,$date_string);
        $do->modify($addendum);
        $this->debug($do, "The plus-one-year value ");
        return $do->format($format);
    }

    /**
     * Basic var_dump function, checks $this->debug_to_screen and spits out to screen if true
     *
     * @param $holder mixed array, object, string, bool - whatever we want to spit out
     * @param $msg string message to put into the screen and debug log
     * @param $die bool kill the script
     */
    private function debug($holder,$msg,$die = FALSE){
        $GLOBALS['log']->debug($msg . print_r($holder,TRUE));
        if($this->debug_to_screen){
            echo "<h3>{$msg}</h3>";
            var_dump($holder);
        }
        if($die) die();
    }

}