- var_dump: documentation ( source)
- explode: documentation ( source)
<?php
$arr=array('0_1','0_3','1_2','1_1','4_1');
$newArray = [];
foreach ($arr as $item) {
$items = explode('_', $item);
$newArray[$items[0]][$items[1]] = $item;
}
var_dump($newArray);
exit();