sort array by multiple keys with optional key - php

Question

The following array contains a sample of data from a larger data set -
$data =
[
[
'readingSequence' => '35',
'bookID' => '19',
'chapter' => '130'
],
[
'readingSequence' => '19',
'bookID' => '19',
'chapter' => '27'
],
[
'readingSequence' => '59',
'bookID' => '19',
'chapter' => '133'
],
[
'readingSequence' => '35',
'bookID' => '19',
'chapter' => '129'
],
[
'readingSequence' => '98',
'bookID' => '75',
'chapter' => '6',
'verses' => '11-20,',
'versesFirst' => '11'
],
[
'readingSequence' => '99',
'bookID' => '75',
'chapter' => '6',
'verses' => '1-10',
'versesFirst' => '1'
]
];
The use case requires that the elements of $data be sorted by bookID, then chapter, then versesFirst if that key exists.
The following code successfully sorts the array by bookID and chapter but I haven't figured out a way to also sort by versesFirst because it is present in some elements but not in others -
array_multisort(array_column($data, 'bookID'), SORT_ASC, array_column($data, 'chapter'), SORT_ASC, $data);
Here is the result:
Array
(
[0] => Array
(
[readingSequence] => 19
[bookID] => 19
[chapter] => 27
)
[1] => Array
(
[readingSequence] => 35
[bookID] => 19
[chapter] => 129
)
[2] => Array
(
[readingSequence] => 35
[bookID] => 19
[chapter] => 130
)
[3] => Array
(
[readingSequence] => 59
[bookID] => 19
[chapter] => 133
)
[4] => Array
(
[readingSequence] => 98
[bookID] => 75
[chapter] => 6
[verses] => 11-20,
[versesFirst] => 11
)
[5] => Array
(
[readingSequence] => 99
[bookID] => 75
[chapter] => 6
[verses] => 1-10
[versesFirst] => 1
)
)
Elements 0 to 3 are sorted correctly but elements 4 and 5 are not because versesFirst is not included. When an attempt was made to include it this warning was displayed and the results looked the same as shown above.
Warning: array_multisort(): Array sizes are inconsistent in C:\development\scratchpad.php on line 122
I could add [versesFirst] => '' to the elements that don't have the versesFirst key so that it could be included in the multisort but I'd rather not resort to that. Is there a way to include optional keys in the multisort? Or is there a different approach entirely to achieve the desired result set?

Answer 1

You can use usort to accomplish this with isset checks for versesFirst key.
Snippet:
<?php
usort($data, function($a,$b){
$book_id_1 = intval($a['bookID']);
$book_id_2 = intval($b['bookID']);
if($book_id_1 != $book_id_2) return $book_id_1 <=> $book_id_2;
$chapter_1 = intval($a['chapter']);
$chapter_2 = intval($b['chapter']);
if($chapter_1 != $chapter_2) return $chapter_1 <=> $chapter_2;
if(!isset($b['versesFirst'])){
return -1;
}
if(!isset($a['versesFirst'])){
return 1;
}
return intval($a['versesFirst']) <=> intval($b['versesFirst']);
});
print_r($data);