php

$array = [
['id' => 1, 'pid' => 0, 'name' => '这是主类'],
['id' => 2, 'pid' => 0, 'name' => '这是主类'],
['id' => 3, 'pid' => 1, 'name' => '父级为1子类'],
['id' => 4, 'pid' => 2, 'name' => '父级为2子类'],
['id' => 5, 'pid' => 3, 'name' => '父级为3子类'],
];

function tree($array, $pid)
{
$tree = array();
foreach ($array as $key => $value) {
if ($value['pid'] == $pid) {
$value['child'] = tree($array, $value['id']);
if (!$value['child']) {
unset($value['child']);
}
$tree[] = $value;
}
}
return $tree;
}

echo "<pre>" . print_r(tree($array, 1), 1) . "</pre>";