- sscanf: documentation ( source)
- var_export: documentation ( source)
<?php
$array = [
'1.1',
'1.2',
'1.3',
'2.1',
'2.2',
'2.3',
'3.1',
'3.2',
];
$result = [];
foreach ($array as $v) {
sscanf($v, '%d', $major);
if (!isset($ref[$major])) {
$result[] = &$ref[$major];
}
$ref[$major][] = $v;
}
var_export($result);