PHP从查询结果构造多维数组

Question

trying to put together a 3-tiered array of term, class, students for a waitlist clearing page. Here is the foreach I am using to create the array, but something is not right. The resulting array isn't right for looping through and making an html table of term > course >student. My foreach looks like this

    foreach ($active_terms as $term) {
    $waitlists[ $term['term_id'] ] = $term;
        foreach ($active_courses as $course) {
            if ( ($course['term_id'] == $term['term_id']) && ($course['students_waitlisted'] > 0) ) {
            $waitlists[ $term['term_id'] ][ $course['course_id'] ] = $course;                   
                    foreach ($waitlisted_reservations as $reservation) {
                        if ( ($term['term_id'] == $reservation['term_id'])
                                && ($course['course_id'] == $reservation['course_id']) ) {
                            $waitlists[ $term['term_id'] ][ $course['course_id'] ][ $reservation['reservation_id'] ] = $reservation;
                        }   
                    }
            }
        }               
}

and the resulting array is close, but looks like this:

Array
(
[1] => Array
    (
        [term_id] => 1
        [term_title] => Summer Session 1
        [term_begin_date] => June 25 2012
        [3] => Array
            (
                [term_id] => 1
                [course_id] => 3
                [course_title] => Biology 1
                [course_student_limit] => 8
                [students_reserved] => 6
                [students_registered] => 0
                [students_waitlisted] => 3
                [175] => Array
                    (
                        [term_id] => 1
                        [course_id] => 3
                        [reservation_id] => 175
                        [reservation_grade_level] => 12
                        [student_sis_id] => 289055
                    )
                [173] => Array
                    (
                        [term_id] => 1
                        [course_id] => 3
                        [reservation_id] => 173
                        [reservation_grade_level] => 08
                        [student_sis_id] => 111988
                    )
            )
    )
[2] => Array
    (
        [term_id] => 2
        [application_id] => 2
        [term_title] => Summer Session 2
        [term_begin_date] => July 23 2012
        [18] => Array
            ( ....

Could someone please point out how I can make the parent-child nest correctly? Or is this array correct, and I've messed up on how to do the nested foreach to build the table?

Answer 1

You have to introduce one more level. For instance, replace:

$waitlists[ $term['term_id'] ][ $course['course_id'] ] = $course;

With this:

$waitlists[ $term['term_id'] ]['courses'][ $course['course_id'] ] = $course;

Update

To keep yourself sane you can also use references in your foreach, like:

foreach ($active_terms as $term) {
$waitlists[ $term['term_id'] ] = $term;
    foreach ($active_courses as $course) {
        if ( ($course['term_id'] == $term['term_id']) && ($course['students_waitlisted'] > 0) ) {
        $waitlists[ $term['term_id'] ][ $course['course_id'] ] = $course;  

Can also be written like:

foreach ($active_terms as $term) {
    $waitlists[ $term['term_id'] ] = $term;
    $current_courses = &$waitlists[ $term['term_id'] ]['courses'];

    foreach ($active_courses as $course) {
        if ( ($course['term_id'] == $term['term_id']) && ($course['students_waitlisted'] > 0) ) {
        $current_courses[ $course['course_id'] ] = $course;  

To shorten the variable names. You can probably work out the rest from there :)