Просто переберите массив, возможно, так:
$input = array(
'Jessica CS' => array(
'2011-04-20' => array(
0 => 69.9,
'cancel' => 1311145200,
1 => 29.95,
2 => 69.90,
),
),
'Rex CS' => array(
'2011-04-20' => array(
0 => 119.94,
'cancel' => null,
),
'2011-04-26' => array(
0 => 199.50,
'cancel' => null,
1 => 29.95,
)
)
);
$totals = array();
foreach($input as $person => $dates){
$totals[$person] = 0;
foreach ($dates as $date => $values) {
foreach ($values as $key => $val) {
if ($key !== 'cancel') {
$totals[$person] += $val;
}
}
}
}
print_r($totals)
Производит:
Array
(
[Jessica CS] => 169.75
[Rex CS] => 349.39
)