Answers for "php sub array by value in object"

slice array php

array_slice() function is used to get selected part of an array.
Syntax:
array_slice(array, start, length, preserve)
*preserve = false (default)
If we put preserve=true then the key of value are same as original array.

Example (without preserve):
<?php
$a=array("red","green","blue","yellow","brown");
print_r(array_slice($a,1,2));
?>

Output:
Array ( [0] => green [1] => blue )
  
Example (with preserve):
<?php
$a=array("red","green","blue","yellow","brown");
print_r(array_slice($a,1,2,true));
?>

Output:
Array ( [1] => green [2] => blue )

php collapse common columns in associative array

/* Collapse on common columns which is also the new key e.g.
([0] => [[id] => 1234, [firstName] => "foo", [1] => [[id] => 1234, [lastName] => "bar")
will become ([1234] => [[firstName] => "foo", [lastName]="bar"]
Credit to https://stackoverflow.com/users/762073/xdazz
*/
$result = array();
foreach ($data as $element) {
    $result[$element['id']][] = $element;// [] appends to the array if it already exists
}