Q:

Group ROWS in array with same Identifier

How can I run this array below inside of a foreach loop and group the rows together that share the same section_id?
I've labeled all the rows and sections with comment blocks.
This is the array
Array ( 
    [0] => Array ( // Row 1
        [assessment_selection_id] => 63 
        [assessment_id] => 32 
        [section_id] => 1 // Section 1
        [question_id] => 1 
        [selection] => 2 
        [timestamp] => 1368160586 
   ) 
   [1] => Array ( // Row 2
        [assessment_selection_id] => 61 
        [assessment_id] => 32 
        [section_id] => 2 // Section 2
        [question_id] => 1 
        [selection] => 3 
        [timestamp] => 1368160510 
   )
   [2] => Array ( // Row 3
        [assessment_selection_id] => 61 
        [assessment_id] => 32 
        [section_id] => 2 // Section 2
        [question_id] => 1 
        [selection] => 3 
        [timestamp] => 1368160510 
   ) 

   [3] => Array ( // Row 4
        [assessment_selection_id] => 61 
        [assessment_id] => 32 
        [section_id] => 2 // Section 2
        [question_id] => 1 
        [selection] => 3 
        [timestamp] => 1368160510 
   ) 
)

Expected result
Array ( 
   [0] => Array ( // Section 1
        [0] => Array ( // Row 1 
            [assessment_selection_id] => 63 
            [assessment_id] => 32 
            [section_id] => 1 
            [question_id] => 1 
            [selection] => 2 
            [timestamp] => 1368160586 
        )
    )
    [1] => Array ( // Section 2
        [0] => Array ( // Row 1
            [assessment_selection_id] => 61 
            [assessment_id] => 32 
            [section_id] => 2 
            [question_id] => 1 
            [selection] => 2 
            [timestamp] => 1368160586 
        )
       [1] => Array ( // Row 2
            [assessment_selection_id] => 61 
            [assessment_id] => 32 
            [section_id] => 2 
            [question_id] => 1 
            [selection] => 2 
            [timestamp] => 1368160586 
        )
       [2] => Array ( // Row 3
            [assessment_selection_id] => 61 
            [assessment_id] => 32 
            [section_id] => 2 
            [question_id] => 1 
            [selection] => 2 
            [timestamp] => 1368160586 
        )
    )
)

Expected result without array
Section 1

Row 1
assessment_selection_id, 
assessment_id, 
section_id, 
question_id, 
selection, 
timestamp

Section 2

Row 1
assessment_selection_id, 
assessment_id, 
section_id, 
question_id, 
selection, 
timestamp
Row 2
assessment_selection_id, 
assessment_id, 
section_id, 
question_id, 
selection, 
timestamp
Row 3
assessment_selection_id, 
assessment_id, 
section_id, 
question_id, 
selection, 
timestamp

A:

Let's think you have your array saved in $myArray
Do this:
$newArray=array();
foreach($myArray as $val){
    $newKey=$val['section_id'];
    $newArray[$newKey][]=$val
}
print_r($newArray);

