Aggregating an array and displaying the aggregation result alongside the detail - php

Question

I have a $department variable, which is an instance of a Department class.
The Department class has a property called $employees that contains an array of Employee instances related to that department (retrieved from the database).
The Employee class has a properties called $salary_amount and $job_type_id. The $employees array elements are ordered together by $job_type_id.
For a specified department, I'm outputting a list of employees in that department like so:
Employees for IT Department
----------------------------
<?php foreach($department->employees as $employee): ?>
<?php echo $employee->name; ?>
<?php echo $employee->salary_amount; ?>
<?php endforeach; ?>
What's an efficient way to manipulate $department->employees so I can display a sum-total of the $salary_amount for each $job_type_id alongside the list of employees?
Employees for IT Department
----------------------------
## Help Desk ##
Joseph Lazar
$47,000
John Q. Smith
$15,444
--> Total Salary for Help Desk: $62,444
## Database Administrator ##
Piet Pietersen
$55,120
Ivan Horvat
$63,750
--> Total Salary for Help Desk: $118,870
Current Approach
Currently, $employees is being populated by a single SQL query, ordering the results how I want. I'm then running a separate SQL query to get an array of $salary sum-totals for each $job_type_id using a technique from another question.
However, the resultset from this 2nd query is stored in a different variable $subtotals. Therefore, I still have the problem of efficiently getting the Sum-Total to display "in-context" with the list of employees.
I happen to be using Yii framework, however that's probably irrelevant unless I should think about or approach this type of problem from a totally different perspective? Please tell me in the comments.
Update 1
Here's the current code I'm using, however it feels messy and like there could be a better way. As mentioned above, the aggregation is done by a separate SQL, however I'm open to alternatives.
<?php
$employee_key = 0;
$employees_count = sizeof($department->employees);
$type_sum_key = 0;
$current_type_in_focus = null;
$next_type_in_focus = null;
foreach($department->employees as $employee)
{
$current_type_in_focus = $employee->job_type_id;
$next_type_in_focus = (isset($department->employees[$employee_key+1])) ? $department->employees[$employee_key+1]->job_type_id : null;
# output individual employee data
echo $employee->name;
echo $employee->salary_amount;
# output aggregated total for job type
if ( $current_type_in_focus !== $next_type_in_focus || $employee_key+1 == $employees_count )
{
echo '--> Total Salary for ' . $employee->jobType->name . ': ' . $department->subtotals[$type_sum_key]->total;
$type_sum_key++;
}
$income_key++;
}
?>

Answer 1

One approach would be to use while loops. For example (for clarity the following code sample does not format the output, also it outputs job_type_id rather than a description as that data is not shown in the question):
$employees = $department->employees;
$employee = current($employees);
while($employee)
{
$job_type_id = $employee->job_type_id;
$total_salary = 0;
echo "## Job Type $job_type_id ##";
while ($employee && $employee->job_type_id == $job_type_id)
{
echo $employee->name;
echo $employee->salary_amount;
$total_salary += $employee->salary_amount;
$employee = next ($employees);
}
echo "-->Total Salary for Job Type $job_type_id: $total_salary";
}