Sorting a list of arrays by its last character in php

Question

In PHP, how might one sort an array by the last characters of its values? Take, for example, the following array:

$string[0] = "They";
$string[1] = "started";
$string[2] = "plotting";
$string[3] = "against";
$string[4] = "him";

After the sort, the array would look like this (note the order based on the last characters of each value... also note the rewritten indexes):

$string[0] = "started";
$string[1] = "plotting";
$string[2] = "him";
$string[3] = "against";
$string[4] = "they";

And where is your own effort to solve this? The topic of [sorting arrays](https://stackoverflow.com/questions/17364127/how-can-i-sort-arrays-and-data-in-php) has been extensively covered. You should have enough information to at least get started. — El_Vanja, Apr 29 '21 at 10:02

score 3 · Accepted Answer · answered Apr 29 '21 at 10:04

3

usort allows a custom sort function to be passed, so you can do:

usort($string , function($a, $b) {
  $aLastChar = substr($a, -1);
  $bLastChar = substr($b, -1);

  return ($aLastChar < $bLastChar) ? -1 : 1;
});

answered Apr 29 '21 at 10:04

thelastshadow

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could u please explain me this usort function..? – Shalu Awzme Apr 29 '21 at 10:16
@ShaluAwzme The php docs I linked to will do a much better job of that than I. – thelastshadow Apr 30 '21 at 10:03

score 0 · Answer 2 · answered Apr 29 '21 at 10:08

You can invert the array value text and use sort as usual, then invert the output again.

Because you are considering the last letter of the words

$strings = [
 "They",
 "started",
 "plotting",
 "against",
 "him",
];
foreach ($strings as $key => $value) {
    $strings[$key] = strrev($value);
}
sort($strings);
foreach ($strings as $key => $value) {
    $strings[$key] = strrev($value);
}
print_r($strings);

Result:

Array
(
    [0] => started
    [1] => plotting
    [2] => him
    [3] => against
    [4] => They
)

PointerBreaker · Answer 3 · 2021-04-29T12:01:17.547

I haven't touched php in a long time, this is not the cleanest solution. But a quick solution is using array_map to reverse all of the strings, followed by calling sort to sort the array, then reversing the array again. A more effective solution would be by writing a custom comparer so you only iterate through the array once; rather than three times.

$string[0] = "They";
$string[1] = "started";
$string[2] = "plotting";
$string[3] = "against";
$string[4] = "him";

$output = array_map('strrev', $string);
sort($output);
$sorted = array_map('strrev', $output);
var_dump($sorted);

Edit: (Cannot comment yet):

Although thelastshadow's solution has less iterations; keep in mind that it'll only compares the last character. So once you have multiples of the same characters the storting becomes incorrect.

Sorting a list of arrays by its last character in php

3 Answers3