<?php

$post = array();
$post['array1'] = array(
    'info1' => 'test 1',
    'info2' => 'test 2',
    'info3' => 'test 3'
);
$post['info4'] = '#';

echo serialize($post);

?>

a:2:{s:6:"array1";a:3:{s:5:"info1";s:6:"test 1";s:5:"info2";s:6:"test 2";s:5:"info3";s:6:"test 3";}s:5:"info4";s:1:"#";}