Array1
    (
        [0] => 2010-06-14
        [1] => 2010-06-14
        [2] => 2010-06-14
        [3] => 2014-01-26
        [4] => 2014-01-26
    )
   Array2
    (
        [0] => 120
        [1] => 100
        [2] => 60
        [3] => 140
        [4] => 30
    )

$date = 2010-06-14;
$value = 280;

$date = 2014-01-26;
$value = 170;

foreach ($values as $key => $value) {
    $result[$dates[$key]] = $value + ($result[$dates[$key]] ?? 0);
}

array (size=2)
  '2010-06-14' => int 280
  '2014-01-26' => int 170

$sum=0;              // New Element
$Array3[][]=0;       // New 2D array

$p=0;                                  // Counter for 2D array
for($i=0;$i<5;$i++)                   // Single loop for traversing
{
$date=Array1[$i];                     // Start for a date
while($date==Array1[$i]){             // For for Similar date
$sum=$sum+Array2[$i];                 // Adding values of similar date
$i++;                                 // Increment array
}
$Array3[$p]["date"]=$date;            // Array3 date element
$Array3[$p]["sum"]=$sum;              // Array4 date element
$i--;                                 // Reducing a value which is incremented in while loop
}

Array3
    (
        [0] => array( 'date' => "  ",'sum' => " ")
        [1] => array( 'date' => "  ",'sum' => " ")
     )

private function forLoopVersion($array1, $array2, $target) {
 $result = 0;
 for ($i = 0; $i < count($array1); ++$i) {
  if ($array1[$i] == $target) {
    $result += $array2[$i];
  }
 }
 return $result;
}

private function foreachLoopVersion($array1, $array2, $target) {
 $result = 0;
 foreach ($array1 as $key => $value) {
  if ($value == $target) {
    $result += $array2[$key];
  }
 }
 return $result;
}

$newArray = array();
for($i = 0; $i < count(Array1); $i++) {
  $newArray[$Array1[$i]] = $Array2[$i];
}

echo $newArray[$date1] + $newArray[$date2];