<?php

$array1 = array(array('login' =>'104',
                      'uid' =>  '1363861889.100'),
                array('login' =>  '131',
                      'uid' =>  '1363863722.126'));

$array2 = array(array('2013', '03', '25', '15', '39', '49', 'anonymous', '1363863722.126'),
                array('2013', '03', '25', '12', '39', '42', 'anonymous', '1363861889.100'));

$array1_inverted = array();
foreach ($array1 as $subarray) {
    $array1_inverted[$subarray['uid']] = $subarray;
}
foreach ($array2 as &$element) {
    $array1_element = $array1_inverted[$element[7]];
    $element['uid'] = $array1_element['uid'];
    $element['login'] = $array1_element['login'];
}

print_r($array2);