Somme un array par clé

la fonction:
<?php
function array_sum_values() {
    $return = array();
    $intArgs = func_num_args();
    $arrArgs = func_get_args();
    if($intArgs < 1) trigger_error('Warning: Wrong parameter count for array_sum_values()', E_USER_WARNING);
    
    foreach($arrArgs as $arrItem) {
        if(!is_array($arrItem)) trigger_error('Warning: Wrong parameter values for array_sum_values()', E_USER_WARNING);
        foreach($arrItem as $k => $v) {
            $return[$k] += $v;
        }
    }
    return $return;
}
script:
$array1 = array('1'=>'1','2'=>'2','3'=>'3');
$array2 = array( '2'=>'1','3'=>'2','4'=>'3');
$array3 = array('3'=>'1','4'=>'22','5'=>'3');
print_r($array1 );
print_r($array2 );
print_r($array3 );
$array  = array_sum_values($array1, $array2, $array3) ;
print_r($array);
?>

$sql = 'SELECT date_debut, date_fin FROM `table`';
$req = mysql_query($sql);
 $business_days=0;
while ($data = mysql_fetch_array($req))
{

   $business_days = $dates->days_diff($data['date_debut'], $data['date_fin']);
}
      echo '<pre>';
$array  = array_sum_values($business_days);

   echo '</pre>';