Get lowest key - array value in multidimensional array PHP - php

Question

So, I got array that looks something like this:
[65]=>
array(2) {
[0]=>
array(2) {
["p"]=>
float(234)
["sp"]=>
float(234)
}
[1]=>
array(2) {
["p"]=>
float(53)
["sp"]=>
float(5)
}
[2]...
[3]...
}
The idea is to go through each of 0 - N values of key 65 array, and only keep one with smallest "p", others should be removed / filtered out.
This should be done in PHP.
Anyone has any idea?
I tried something like this:
$array = array_filter($array, function ($value, $key) use ($a) {
return $a['p'] <= $value['p'];
}, ARRAY_FILTER_USE_BOTH);
where $value is 1 of elements inside 65 keyed-array and $a is current pair that is being added dynamically. So when ever its added, I go through existing elements and if its lowest, it should stay, and others get instant filtered out, but if its higher, it should automatically be filtered out.
Thank you!

Answer 1

You can use array_reduce() to get the lowest "p"-value:
$arr = [
65 => [
["p" => 234, "sp" => 234],
["p" => 53, "sp" => 5],
["p" => 530, "sp" => 5],
]
];
function getLowestKey($carry, $item) {
if ($item['p'] < $carry || !$carry) {
$carry = $item['p'];
}
return $carry;
}
$lowestKey = array_reduce($arr[65], 'getLowestKey');
var_dump($lowestKey); // int(53)
Edit:
I just noticed there is a second part to your question, sorry about that. Once you found out the "lowest p" you can then just filter the array with that knowledge:
$lowestPs = array_filter($arr[65], function($item) use ($lowestKey) {
return $item['p'] == $lowestKey;
});
var_dump($lowestPs);
/*
array(2) {
[1]=>
array(2) {
["p"]=>
int(53)
["sp"]=>
int(5)
}
[2]=>
array(2) {
["p"]=>
int(53)
["sp"]=>
int(5)
}
}
*/
This solution works even if multiple entries have the same lowest "p" value (like 53 in the above example), all of those will stay.

Answer 2

Use array_column() to do an array_multisort() on the 'p' value for the records inside key 65.
<?php
$col = 'p'; // set the column you want to order on
$column = array_column($arr[65], $col);
array_multisort($column, SORT_ASC, $arr[65]);
$arr[65] = $arr[65][0]; // only keep the record with lowest 'p' value
demo

Answer 3

If have more than 1 nested levels, you might also use a recursive approach checking the value of p, keeping the array with the lowest value.
$arrays = [
65 => [
["p" => 234, "sp" => 234],
[
["p" => 53,"sp" => 5],
[
["p" => 54,"sp" => 1],
["p" => 53,"sp" => 7],
]
], [
"p" => 255,
"sp" => 235
],
]
];
function loop($array, &$coll = [], &$min = null)
{
foreach ($array as $key => $value) {
if (is_array($value)) {
loop($value, $coll, $min);
} elseif ($key === "p") {
if ($min === null) $min = $value;
if ($min > $value) {
$coll = [$array];
$min = $value;
continue;
}
if($value === $min) $coll[] = $array;
}
}
return $coll;
}
$arrays[65] = loop($arrays[65]);
var_dump($arrays);
Output
array(1) {
[65]=>
array(2) {
[0]=>
array(2) {
["p"]=>
int(53)
["sp"]=>
int(5)
}
[1]=>
array(2) {
["p"]=>
int(53)
["sp"]=>
int(7)
}
}
}
See another php demo.