Group objects in an array of objects by a column value and create a subarray of objects in each group

Question

I have the following query result:

Array
(
    [0] => stdClass Object
        (
            [TreatmentLog_ID] => 131
            [DateAdministered] => 2016-07-15
            [Notes] => 
            [Treatment_ID] => 144
            [AmountAdministered] => 1.5
            [Injectable_ID] => 2
            [InjectableName] => Baytril
        )

    [1] => stdClass Object
        (
            [TreatmentLog_ID] => 133
            [DateAdministered] => 2016-07-12
            [Notes] => 
            [Treatment_ID] => 146
            [AmountAdministered] => 1.2
            [Injectable_ID] => 20
            [InjectableName] => Vitamin C
        )

    [2] => stdClass Object
        (
            [TreatmentLog_ID] => 133
            [DateAdministered] => 2016-07-12
            [Notes] => 
            [Treatment_ID] => 147
            [AmountAdministered] => 1.3
            [Injectable_ID] => 21
            [InjectableName] => Vitamin E
        )
)

I'd like to be able to restructure the array into something like this:

Array
(
    [0] => stdClass Object
        (
            [TreatmentLog_ID] => 131
            [DateAdministered] => 2016-07-15
            [Notes] => 
            [Treatments] => Array
                (
                    [0] => stdClass Object
                        (
                            [Treatment_ID] => 144
                            [AmountAdministered] => 1.5
                            [Injectable_ID] => 2
                            [InjectableName] => Baytril
                        )

                )

        )

    [1] => stdClass Object
        (
            [TreatmentLog_ID] => 133
            [DateAdministered] => 2016-07-12
            [Notes] => 
            [Treatments] => Array
                (
                    [0] => stdClass Object
                        (
                            [Treatment_ID] => 146
                            [AmountAdministered] => 1.2
                            [Injectable_ID] => 20
                            [InjectableName] => Vitamin C
                        )

                    [1] => stdClass Object
                        (
                            [Treatment_ID] => 147
                            [AmountAdministered] => 1.3
                            [Injectable_ID] => 21
                            [InjectableName] => Vitamin E
                        )

                )

        )

)

Notice how the second array looks merges the InjectableName, AmountAdministered, Injectable_ID, and Treatment_ID into the array Treatments if the TreatmentLog_ID is a match. Typically working with arrays isn't a problem, but this one has me stumped. Also I cannot change the query.

How could I pull this off in PHP?

where does this item [InjectableTypeName] come from? It doesn't exist in your initial array — RomanPerekhrest
– RomanPerekhrest, Commented Jul 17, 2016 at 12:54
@RomanPerekhrest It's irrelevant data that was excluded from my query. — Shaazaam
– Shaazaam, Commented Jul 17, 2016 at 13:02

RomanPerekhrest · Accepted Answer · 2016-07-17 13:30:58Z

1

The solution using isset and array_values functions:

// $arr is your initial array
$result = [];
foreach ($arr as $obj) {
    $innerObj = (object)[ 'Treatment_ID' => $obj->Treatment_ID, 'AmountAdministered' => $obj->AmountAdministered,
                          'Injectable_ID' => $obj->Injectable_ID, 'InjectableName' => $obj->InjectableName ];

    if (!isset($result[$obj->TreatmentLog_ID])) {
        $result[$obj->TreatmentLog_ID] = (object)[
            'TreatmentLog_ID' => $obj->TreatmentLog_ID,
            'DateAdministered' => $obj->DateAdministered,
            'Notes' => $obj->Notes,
            'Treatments' => [$innerObj]
        ];
    } else {
        $result[$obj->TreatmentLog_ID]->Treatments[] = $innerObj;
    }
}

$result = array_values($result);
print_r($result);  // will output the expected result

edited Jul 17, 2016 at 13:30

answered Jul 17, 2016 at 13:25

RomanPerekhrest

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Comments

Will · Accepted Answer · 2016-07-19 19:38:57Z

Try this.

We use array_filter() to fetch all of the elements from the $inputArray with the same TreatmentLog_ID. Then we transform those filtered elements with array_map(). We have to create a copy of each element with clone, since they're objects and objects are passed by reference. Then we unset() the keys we don't need in the copy.

<?php

$inputArray = [
    0 => (object) [
        'TreatmentLog_ID' => 131,
        'DateAdministered' => '2016-07-15',
        'Notes' => '',
        'Treatment_ID' => 144,
        'AmountAdministered' => 1.5,
        'Injectable_ID' => 2,
        'InjectableName' => 'Baytril'
    ],

    1 => (object) [
        'TreatmentLog_ID' => 133,
        'DateAdministered' => '2016-07-12',
        'Notes' => '',
        'Treatment_ID' => 146,
        'AmountAdministered' => 1.2,
        'Injectable_ID' => 20,
        'InjectableName' => 'Vitamin C'
    ],

    2 => (object) [
        'TreatmentLog_ID' => 133,
        'DateAdministered' => '2016-07-12',
        'Notes' => '',
        'Treatment_ID' => 147,
        'AmountAdministered' => 1.3,
        'Injectable_ID' => 21,
        'InjectableName' => 'Vitamin E'
    ],
];

$transformedArray = [];
foreach ($inputArray as $key => $value)
{
    $transformedArray[$key] = [
        'TreatmentLog_ID' => $value->TreatmentLog_ID,
        'DateAdministered' => $value->DateAdministered,
        'Notes' => $value->Notes,
        'Treatments' => array_map(
            function ($v) {
                $copy = clone $v;

                unset($copy->Notes);
                unset($copy->DateAdministered);
                unset($copy->TreatmentLog_ID);

                return $copy;
            },
            array_filter($inputArray, function ($v) use ($value) {
                return $v->TreatmentLog_ID == $value->TreatmentLog_ID;
            })
        )
    ];
}

var_dump($transformedArray);

This gives me:

array(3) {
  [0]=>
  array(4) {
    ["TreatmentLog_ID"]=>
    int(131)
    ["DateAdministered"]=>
    string(10) "2016-07-15"
    ["Notes"]=>
    string(0) ""
    ["Treatments"]=>
    array(1) {
      [0]=>
      object(stdClass)#5 (4) {
        ["Treatment_ID"]=>
        int(144)
        ["AmountAdministered"]=>
        float(1.5)
        ["Injectable_ID"]=>
        int(2)
        ["InjectableName"]=>
        string(7) "Baytril"
      }
    }
  }
  [1]=>
  array(4) {
    ["TreatmentLog_ID"]=>
    int(133)
    ["DateAdministered"]=>
    string(10) "2016-07-12"
    ["Notes"]=>
    string(0) ""
    ["Treatments"]=>
    array(2) {
      [1]=>
      object(stdClass)#6 (4) {
        ["Treatment_ID"]=>
        int(146)
        ["AmountAdministered"]=>
        float(1.2)
        ["Injectable_ID"]=>
        int(20)
        ["InjectableName"]=>
        string(9) "Vitamin C"
      }
      [2]=>
      object(stdClass)#7 (4) {
        ["Treatment_ID"]=>
        int(147)
        ["AmountAdministered"]=>
        float(1.3)
        ["Injectable_ID"]=>
        int(21)
        ["InjectableName"]=>
        string(9) "Vitamin E"
      }
    }
  }
  [2]=>
  array(4) {
    ["TreatmentLog_ID"]=>
    int(133)
    ["DateAdministered"]=>
    string(10) "2016-07-12"
    ["Notes"]=>
    string(0) ""
    ["Treatments"]=>
    array(2) {
      [1]=>
      object(stdClass)#8 (4) {
        ["Treatment_ID"]=>
        int(146)
        ["AmountAdministered"]=>
        float(1.2)
        ["Injectable_ID"]=>
        int(20)
        ["InjectableName"]=>
        string(9) "Vitamin C"
      }
      [2]=>
      object(stdClass)#9 (4) {
        ["Treatment_ID"]=>
        int(147)
        ["AmountAdministered"]=>
        float(1.3)
        ["Injectable_ID"]=>
        int(21)
        ["InjectableName"]=>
        string(9) "Vitamin E"
      }
    }
  }
}

Let's break down how we build Treatments:

'Treatments' => array_map(
    function ($v) {
        $copy = clone $v;

        unset($copy->Notes);
        unset($copy->DateAdministered);
        unset($copy->TreatmentLog_ID);

        return $copy;
    },
    array_filter($inputArray, function ($v) use ($value) {
        return $v->TreatmentLog_ID == $value->TreatmentLog_ID;
    })
)

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