get an array element where another element is known? - php

Question

Array
(
[0] => Array
(
[what] => b4
[map] => 74,76,77,83
)
[1] => Array
(
[what] => b2
[map] => 53,82
)
[2] => Array
(
[what] => b1
[map] => 36
)
)
abc('b4');
function abc($what){
$map = // element `map` where `what` = $what;
}
So I need to get map where what is equal to $what;
For example - if $what is b4 result should be 74,76,77,83; and so on.
How can I do this?

Answer 1

If you are going to access the data on a regular basis and the what is unique, then use array_column() with the third parameter as the column to use as the key. Then your array is easily access with what and no loops are harmed in this answer...
$array = Array
(
Array
(
"what" => "b4",
"map" => "74,76,77,83"
),
Array
(
"what" => "b2",
"map" => "53,82"
),
Array
(
"what" => "b1",
"map" => "36"
)
);
$array = array_column($array, null, "what");
echo $array['b4']['map'];
gives...
74,76,77,83

Answer 2

With array_search() and array_column() you can get the matching $map in one line:
<?php
$array = Array
(
Array
(
"what" => "b4",
"map" => "74,76,77,83"
),
Array
(
"what" => "b2",
"map" => "53,82"
),
Array
(
"what" => "b1",
"map" => "36"
)
);
function abc($array, $what) {
return $array[array_search($what, array_column($array, 'what'))]['map'];
}
echo abc($array, "b4");
The function de-constructed and explained:
function abc($array /* the complete input array */, $what /* the search string */) {
// get the key of the sub-array that has $what in column 'what':
$key = array_search($what, array_column($array, 'what'));
// use that key to get 'map' on index $key
return $array[$key]['map'];
}
A working fiddle can be found here: https://3v4l.org/0NpcX

Answer 3

I think "walking" through an array is easy to read and understand:
<?php
$map = [
[
'what' => "b4",
'map' => "74,76,77,83"
],
[
'what' => "b2",
'map' => "53,82"
],
[
'what' => "b1",
'map' => "36"
]
];
function lookupWhatInMap(&$map, $what) {
array_walk($map, function($entry, $key) use ($what) {
if ($entry['what'] == $what) {
print_r($entry['map']);
}
});
}
lookupWhatInMap($map, "b4");

Answer 4

All you have to do is loop through your map and compare values.
function abc($what){
$map = [...];
foreach($map as $item) {
if (isset($item[$what]) ) {
return $item["map"];
}
}
return false;
}

Answer 5

If you just want 1 value from the array, you could use a foreach and a return statement where there is a match:
$a = [
[
"what" => "b4",
"map" => "74,76,77,83"
],
[
"what" => "b2",
"map" => "53,82"
],
[
"what" => "b1",
"map" => "36"
]
];
function abc($what, $arrays)
{
foreach ($arrays as $array) {
if ($array['what'] === $what) {
return $array['map'];
}
}
return false;
}
echo(abc('b4', $a)); // 74,76,77,83
Demo

Answer 6

https://ideone.com/V9WNNx
$arr[] = [
'what' => 'b4',
'map' => '74,76,77,83'
];
$arr[] = [
'what' => 'b2',
'map' => '53,82'
];
$arr[] = [
'what' => 'b1',
'map' => '36'
];
echo abc('b4', $arr);
function abc($what, $arr){
$map = null;
$idx = array_search($what, array_column($arr, 'what'));
if ($idx !== false) {
$map = $arr[$idx]['map'];
}
return $map;
}