php creating multi-dimension array from single array

this is simple example.

$head = array("id">1,"name"=>"Harshana","servents"=>array(
"s1"=>array("id">1,"name"=>"abc"),
"s2"=>array("id">2,"name"=>"sdf"),
"s3"=>array("id">3,"name"=>"fgh")
));
print_r($head);
echo "<hr />";
print_r($head["servents"]);
echo "<hr />";
print_r($head["servents"]["s1"]);
echo "<hr />";
$s1 = $head["servents"]["s1"];
echo "servent 1 name :".$s1["name"];

hope you can get idea for your matter.

I have attempted to solve your problem. I have made 3 functions to keep the responsibilities for each function down to a minimum. It looks like the following:

function build_employee_hierarchy(array $employees) {

    $groups    = build_employee_groups($employees);
    $hierarchy = build_employee_group_inheritance($employees, $groups);

    return $hierarchy[0];

}

function build_employee_group_inheritance(array $employees, array $groups) {

    $hierarchy = [];

    foreach($employees as $key => $employee) {

        $employee_id     = $employee['id'];
        $hierarchy[$key] = $employee;

        if(!array_key_exists($employee_id, $groups)) {
            continue;
        }

        $hierarchy[$key]['staff'] = build_employee_group_inheritance($groups[$employee_id], $groups);

    }

    return $hierarchy;
}

function build_employee_groups(array $employees) {

    $groups = [];

    foreach($employees as $employee) {

        if(array_key_exists('line-manager', $employee) && !is_null($employee['line-manager'])) {

            $groups[$employee['line-manager']][] = $employee;

        }

    }

    return $groups;

}

These functions first group all employees who belong to the same line manager. Then the inheritance of the employees is resolved recursively. The function build_employee_hierarchy serves as a utility method for building the whole hierarchy by providing a single array.

With the data you provided the result will look like the following. The only difference is that when there is no line manager it equals NULL instead of the string none.

array (size=4)
  'id' => int 1
  'name' => string 'Miriam Wood' (length=11)
  'line-manager' => null
  'staff' => 
    array (size=2)
      0 => 
        array (size=3)
          'id' => int 2
          'name' => string 'Alan Haworth' (length=12)
          'line-manager' => int 1
      1 => 
        array (size=4)
          'id' => int 3
          'name' => string 'Guy Kahane' (length=10)
          'line-manager' => int 1
          'staff' => 
            array (size=2)
              0 => 
                array (size=3)
                  'id' => int 4
                  'name' => string 'Matthew Baum' (length=12)
                  'line-manager' => int 3
              1 => 
                array (size=3)
                  'id' => int 5
                  'name' => string 'Rebecca Roache' (length=14)
                  'line-manager' => int 3

This may not be the most efficient solution, but because if uses recursion the array can be a long as you like.

OBS

If the data comes from a relational database there is most likely a much more efficient way to retrieve the data in the same form by using the SQL language the database uses. If that is the case ask the awesome people at Database Administrators (Stackexchange).

Hope this helps.