Custom order array in PHP - php

Question

I got this array:
$array = array('E1211','E2172','E2181','E233','E241','E286');
And I need to order first by first number-letter, i.e. E1, E2, E3, E4... followed by ordered numbers from lowest to highest.
Desired order would be: E1211, E233, E241, E286, E2172, E2181
If i do sort($array); the order will will be: "E1211", "E2172", "E2181", "E233", "E241" "E286".
If i do natsort($array); it will order by numbers from lowest to higest: "E233", "E241", "E286", "E1211", "E2172", "E2181"

Answer 1

Use usort() with a custom comparison function to split the strings and compare the portions.
<?php
$array = array('E1211','E2172','E2181','E233','E241','E286');
usort($array, function($a, $b){
$pfxA = substr($a,0,2); // Get the first two characters of each string
$pfxB = substr($b,0,2);
if ( $pfxA !== $pfxB) {return $pfxA<=>$pfxB;} // If they're not equal, return the spaceship comparison
return (int)substr($a,2)<=>(int)substr($b,2); // Prefixes are equal. Convert the rest to integers and return the spaceship comparison.
});
var_dump($array);
Output:
array(6) {
[0]=>
string(5) "E1211"
[1]=>
string(4) "E233"
[2]=>
string(4) "E241"
[3]=>
string(4) "E286"
[4]=>
string(5) "E2172"
[5]=>
string(5) "E2181"
}
See https://3v4l.org/5qts5

Answer 2

Actually what you want to do is mixing sorting with your own pattern with natsort(). I doubt if it can be accomplished by some oneliner, however it can be done with simple iteration in separate steps, that code does what I think you want (input data modified for better readibility).
<?php
$array = ['E3123', 'E1211', 'E2181', 'E241', 'E286', 'E2172', 'E233'];
$newArray = [];
$finalArray=[];
// Put it into associative array with required keys (two first chars)
foreach ($array as $item) {
$key = substr($item, 0, 2);
$newArray[$key][] = $item;
}
// sort new array by key (two first chars)
ksort($newArray);
// sort each subarray in natural order and put it to final array
foreach ($newArray as $key => $newItem) {
natsort($newArray[$key]);
$finalArray = array_merge($finalArray, $newArray[$key]);
}
// just check
var_dump($finalArray);
Result:
array (size=7)
0 => string 'E1211' (length=5)
1 => string 'E233' (length=4)
2 => string 'E241' (length=4)
3 => string 'E286' (length=4)
4 => string 'E2172' (length=5)
5 => string 'E2181' (length=5)
6 => string 'E3123' (length=5)