Simplify value localization in arrays in PHP

Question

I have the arrays as below:

$records = [
    ["id"=>"1", "name"=>"Alpha"],
    ["id"=>"2", "name"=>"Bravo"],
    ["id"=>"3", "name"=>"Charlie"],
    ["id"=>"4", "name"=>"Delta"],
    ["id"=>"5", "name"=>"Echo"],
];

$codes = [2,4];

I need to print only the names contained in the variable $records corresponding to each variable code $codes awaiting the outcome:

Bravo

Delta

So I made the following code:

foreach ($codes as $i) {
    foreach ($records as $j) {
        if ($i == $j['id']) {
            echo "<p> {$j['name']} </p>";
        }
    }
}

Is there any way to get the same result easier?

I found it bad the way I’m doing because for each variable code $codes i do a full scan on variable $records comparing the values.

Answer 1

whereas the value of id is unique for each name, you can define a map that relates the id to the respective name. In PHP, we can define this map through a array associative in which the key is id and the value is its name. We can mount this map with a line of code:

$nomes = array_column($records, "name", "id");

This will generate the array:

Array
(
    [1] => Alpha
    [2] => Bravo
    [3] => Charlie
    [4] => Delta
    [5] => Echo
)

Thus, it would be enough to access the positions $nomes[2] and $nomes[4], or:

foreach ($codes as $code) {
    echo $nomes[$code], PHP_EOL;
}

Displaying the desired names.

Answer 2

Could use array_filter to filter information and in_array to search if there is a similar code, example:

<?php

$records = [
    ["id"=>"1", "name"=>"Alpha"],
    ["id"=>"2", "name"=>"Bravo"],
    ["id"=>"3", "name"=>"Charlie"],
    ["id"=>"4", "name"=>"Delta"],
    ["id"=>"5", "name"=>"Echo"],
];

$codes = [2,4];


$array_result = array_filter($records, function($item) use ($codes) {
    return in_array($item['id'], $codes);
});


foreach($array_result as $value){
    echo $value['name'];
}

IDEONE ONLINE EXAMPLE

Answer 3

Use array_filter+foreach and use array_search+array_column+foreach is no better than what you have already asked in your question, which are only 2 foreachs+if, not only of performance, but even of readability of the code, that in the code of the question this best. The use of array_search, array_filter and other functions will not always be better than making 1 or 2 loops, sometimes it will be the same thing, in the case of the Anderson example, the use of array_collunm was the most efficient speaking of the specific function

Still not necessarily the most efficient way in general.

Most often the simplest is the best, and in the case of the need of the author of the question a in_array and a single foreach would already solve everything and keep the code still more readable:

$records = [
    ["id"=>"1", "name"=>"Alpha"],
    ["id"=>"2", "name"=>"Bravo"],
    ["id"=>"3", "name"=>"Charlie"],
    ["id"=>"4", "name"=>"Delta"],
    ["id"=>"5", "name"=>"Echo"],
];

$codes = [2,4];

foreach ($records as $j) {
    if (in_array($j['id'], $codes)) {
        echo "<p> {$j['name']} </p>";
    }
}

Example: https://ideone.com/UFXWqO

Answer 4

Can use array_search (array search) and array_column (search for a specific column):

foreach ($codes as $i) {
   echo "<p> {$records[array_search($i, array_column($records, 'id'))]['name']} </p>";
}

It will fetch in the column id the values of the array $codes and return the key value name.

The array_search($i, array_column($records, 'id')) will return the index of the item in the array $records where the key id matches the array values $codes. It would be like:

> $records[1]['name']
> $records[3]['name']

Check on IDEONE

It will only work in PHP version 5.5 onwards because of array_column.