Why am I getting HTTP: 500 Internal Server Error when I am trying to use after_retrieve?

$hook_array{'after_retrieve'] = Array();

<?php

global $db, $sugar_config;

class Courses_Logic_Hooks {

  //Set field: name
  public function Set_Course_Name(&$focus, $action, $args = array())
  {
    $focus->name = $focus->course_name_c;
  }

  //Set field: curriculum_type
  //No longer used, but kept for reference. Now replaced via /custom/extension/lev_courses/vardefs/sugarfield_curriculum_type.php
  public function Set_Curriculum_Type(&$focus, $action, $args = array())
  {
      require_once('modules/Lev_Course_Catalog/Lev_Course_Catalog.php');
      $course_catalog = new Lev_Course_Catalog();
      $ctype =$course_catalog->retrieve($focus->lev_course_catalog_id_c);
      $focus->curriculum_type =  preg_replace('/[_]/', ' ', $ctype->curriculum_type);

  }

  //Set field: start_date and start_day_of_week
  public function Set_Start_Date(&$focus, $action, $args = array())
  {
      $sql = <<<SQL
SELECT coursedate.class_date AS first_class_date FROM lev_course_class_dates coursedate
      LEFT JOIN lev_courses_lev_course_class_dates_c connect ON coursedate.id=connect.lev_courses_lev_course_class_dateslev_course_class_dates_idb AND coursedate.deleted=0
      LEFT JOIN lev_courses course on connect.lev_courses_lev_course_class_dateslev_courses_ida=course.id and connect.deleted=0
      WHERE course.deleted=0 AND course.id='{$focus->id}' ORDER BY coursedate.class_date ASC LIMIT 1
SQL;

      $result = $GLOBALS['db']->query($sql);
      while ($row = $GLOBALS['db']->fetchByAssoc($result))
      {
        $focus->start_date = $row['first_class_date'];
        $focus->start_day_of_week = date('l', strtotime($row['first_class_date']));
      }
  }

  //Set field: end_date and end_day_of_week
  public function Set_End_Date(&$focus, $action, $args = array())
  {
      $sql = <<<SQL
SELECT coursedate.class_date AS last_class_date FROM lev_course_class_dates coursedate
      LEFT JOIN lev_courses_lev_course_class_dates_c connect ON coursedate.id=connect.lev_courses_lev_course_class_dateslev_course_class_dates_idb AND coursedate.deleted=0
      LEFT JOIN lev_courses course on connect.lev_courses_lev_course_class_dateslev_courses_ida=course.id and connect.deleted=0
      WHERE course.deleted=0 AND course.id='{$focus->id}' ORDER BY coursedate.class_date DESC LIMIT 1
SQL;

      $result = $GLOBALS['db']->query($sql);
      while ($row = $GLOBALS['db']->fetchByAssoc($result))
      {
        $focus->end_date = $row['last_class_date'];
        $focus->end_day_of_week = date('l', strtotime($row['last_class_date']));
      }
  }

  //Set field: academic_period
  public function Set_Academic_Period(&$focus, $action, $args = array())
  {
      if (!empty($focus->start_date))
      {
        if (date('Y', strtotime($focus->start_date)) < '2013')
        {
          if (date('n', strtotime($focus->start_date)) < 5)
          {
            $affix = '21';
          }
          else if (date('n', strtotime($focus->start_date)) < 9)
          {
            $affix = '25';
          }
          else
          {
            $affix = '29';
          }
        }
        else
        {
          $affix = '00';
        }
        $focus->academic_period = date('Y', strtotime($focus->start_date)).$affix;
      }
  }

  //Set field: total_client_fee
  public function Set_Total_Fee(&$focus, $action, $args = array())
  {
      if ($focus->all_inclusive_fee == 1)
      {
        $focus->total_client_fee = $focus->targeted_fee;
      }
      else
      {
        //Get sum of "Total to Client" field from all linked Course Costs
        $sql = <<<SQL
SELECT sum(cost_c.total_to_client_c) AS total_to_client 
FROM lev_course_costs cost
LEFT JOIN lev_course_costs_cstm cost_c
    ON cost.id = cost_c.id_c and cost.deleted =0
LEFT JOIN lev_courses_lev_course_costs_c connect 
    ON cost.id=connect.lev_courses_lev_course_costslev_course_costs_idb 
    AND cost.deleted=0
 LEFT JOIN lev_courses course 
    ON connect.lev_courses_lev_course_costslev_courses_ida=course.id 
    AND connect.deleted=0
WHERE course.deleted=0 AND course.id='{$focus->id}'
SQL;

        $result = $GLOBALS['db']->query($sql);
        while ($row = $GLOBALS['db']->fetchByAssoc($result))
        {
          $total_to_client = $row['total_to_client'];
        }

        $focus->total_client_fee = $focus->targeted_fee + $total_to_client;
      }
  }

  //Set field: total_expense
  public function Set_Total_Course_Expense(&$focus, $action, $args = array())
  {
      //Get sum of "Total to CBT" field from all linked Course Costs
      $sql = <<<SQL
SELECT sum(cost_c.total_expense_c) AS total_cbt 
FROM lev_course_costs cost
LEFT JOIN lev_course_costs_cstm cost_c
    ON cost.id = cost_c.id_c and cost.deleted = 0
LEFT JOIN lev_courses_lev_course_costs_c connect 
    ON cost.id=connect.lev_courses_lev_course_costslev_course_costs_idb 
    AND cost.deleted=0
LEFT JOIN lev_courses course 
    ON connect.lev_courses_lev_course_costslev_courses_ida=course.id 
    AND connect.deleted=0
WHERE course.deleted=0 AND course.id='{$focus->id}'
SQL;

      $result = $GLOBALS['db']->query($sql);
      while ($row = $GLOBALS['db']->fetchByAssoc($result))
      {
        $total_cbt = $row['total_cbt'];
      }

      $focus->total_expense = ((
      (!empty($focus->contact_hours) ? $focus->contact_hours : 0) 
      + 
      (!empty($focus->prep_hours) ? $focus->prep_hours : 0)
      ) * 
      (!empty($focus->hourly_fee_to_instructor) ? $focus->hourly_fee_to_instructor : 0) 
      ) + (
      (!empty($focus->lunch_vouchers) ? $focus->lunch_vouchers : 0) 
      * 
      (!empty($focus->lunch_voucher_amt) ? $focus->lunch_voucher_amt : 0)
      ) + 
      (!empty($total_cbt) ? $total_cbt : 0);
  }

  //Set field: course_net
  public function Set_Course_Net(&$focus, $action, $args = array())
  {
      $focus->course_net = $focus->total_client_fee - $focus->total_expense;
  }


  //Set field: gross_margin
  public function Set_Gross_Margin_Percent(&$focus, $action, $args = array())
  {
      if($focus->total_client_fee == '' || $focus->total_client_fee == 0){
          $focus->gross_margin = 0;
      } else {
          $focus->gross_margin = $focus->course_net / $focus->total_client_fee * 100;
      }
  }

  //Set a request variable for contract id (lev_contracts_lev_courseslev_contracts_ida)
  public function Set_Request_ContractID(&$focus, $action, $args = array())
  {
      //Get sum of "Total to CBT" field from all linked Course Costs
      $sql = <<<SQL
SELECT  account_id_c, accounts.name as company_name FROM lev_contracts
INNER JOIN accounts on accounts.id = lev_contracts.account_id_c
      WHERE lev_contracts.deleted=0 AND lev_contracts.id='{$focus->lev_contracts_lev_courseslev_contracts_ida}'
SQL;
      $result = $GLOBALS['db']->query($sql);
      while ($row = $GLOBALS['db']->fetchByAssoc($result))
      {
        $_POST['lev_contract_name'] = $row['company_name'];
      }
  }



          function setAlertField($bean, $event, $arguments)
        {
            $sql = <<<SQL
            SELECT contract.contract_status AS status FROM lev_contracts contract
                  LEFT JOIN lev_contracts_lev_courses_c connect ON contract.id=connect.lev_contracts_lev_courseslev_contracts_ida AND contract.deleted=0 AND (contract.contract_status = 'Proposal_Active' OR contract.contract_status = 'Proposal_Rejected')
                  LEFT JOIN lev_courses course on connect.lev_contracts_lev_courseslev_courses_idb=course.id and connect.deleted=0
                  WHERE course.deleted=0 AND course.id='{$bean->id}'
SQL;
                  $result = $GLOBALS['db']->query($sql);
                  $bean->alertfield_c = '';
                  while ($row = $GLOBALS['db']->fetchByAssoc($result))
                  {
                    $bean->alertfield_c = '<pre style="border:2px solid #c00; padding: 5px;margin: 5px; color:#0000CC; text-align: center; width: 100%; text-decoration: bold;"> COURSE HAS BEEN BILLED - PLEASE BE CAUTIOUS WHEN MAKING CHANGES</pre>';
                  }
        }


  //check for completed courses and change CSS
  public function Completed_Course($bean, $action, $args = array()){
    //fire on detail view and edit view
    if (($_REQUEST['action'] == 'DetailView' || $_REQUEST['action'] == 'EditView' && $_REQUEST['module'] == 'Lev_Courses') && $_POST['lev_course_completed'] == 'yes')
    {
        echo '<script src="custom/Resources/javascript/Lev_Courses/completedCourse.js" type="text/javascript"></script>';
    }


   }

  //save parent contract to finish the calculations and auto populate fields
    public function saveParentCourse($bean, $event, $args){
        //check if any total field is updated
        if(($bean->total_client_fee !=$bean->fetched_row['total_client_fee'] ) || ($bean->total_expense !=$bean->fetched_row['total_expense'] ) ){
            $parent_contract = $bean->get_linked_beans('lev_contracts_lev_courses','Lev_Contracts');

            if($parent_contract[0]->id !=''){

                    require_once('modules/Lev_Contracts/Lev_Contracts.php');
                    $lev_contract = new Lev_Contracts();
                    $lev_contract->retrieve($parent_contract[0]->id);
                    $lev_contract->save();
                    //$parent_contract = $lev_course->get_linked_beans('lev_courses_lev_course_costs','Lev_Course_Costs');

            }

        }

    }

  //calculate all totals and date after related bean is deleted
  public function update_Course_Data($bean, $event, $args){
      //save bean to calauclate all auto populated fields
      $bean->save();
  }



    function Check_Hourly_Fee(&$bean, $event, $arguments)
    {

        $result = true;
        if (!empty($bean->contact_id_c))
        {
            $getInstructor = new Contact();
            $getInstructor->retrieve($bean->contact_id_c);

	    if (!empty($getInstructor->instructor_pay_rate_max_c))  // Added this check because it was returning false when there was no max pay rate set - 9/5/2012 Adam Canova
	    {
                if ($bean->hourly_fee_to_instructor > $getInstructor->instructor_pay_rate_max_c)
                {
                    $result = false;
                }
	    }
        }


        if($result) {
            return true; //let save proceed as normal
        }

        $_SESSION['myError'] = 'Hourly Fee to Instructor must not exceed the Instructor\'s Maximum Pay Rate';
        //build the URL to return to
        $module = $_REQUEST['module'];
        $action = "&action=EditView"; //we need to have EditView b/c that is the action we are taking
        $returnModule = "&return_module=" . $_REQUEST['return_module'];

        $offset = $_REQUEST['offset'];
        if ($offset == "") {
        } else {
            $offset = "&offset=$offset";
        }

        $stamp = $_REQUEST['stamp'];
        if ($stamp == "") {
        } else {
            $stamp = "&stamp=$stamp";
        }

        if ($recordId == "") {
            $returnAction = "&return_action=DetailView";
        } else {
            $recordId = "&record=" . $recordId;
        }

        $url = "index.php?module=" . $module . $offset . $stamp . $action . $returnModule . $returnAction . $recordId;
        header("Location: $url");
        $_SESSION['Lev_CoursesBean'] = $bean; //store the bean in session so we can retrieve the values later
        exit; //goto the location contained in header
    }

    function Check_Course_Status(&$bean, $event, $arguments)
    {

    }
}

?>