Question

I am learning to program in php and I have a little problem.
I have two arrays:
Array A:

array(10){
           [0]: string(10) "2012-08-01"
           [1]: int 1
           [2]: string(10) "2012-08-03"
           [3]: int 1
           [4]: string(10) "2012-08-07"
           [5]: int 2
           [6]: string(10) "2012-08-09"
           [7]: int 2
           [8]: string(10) "2012-08-27"
           [9]: int 1
          }

Array B:

array(4){
          [0]: string(10) "2012-09-04"
          [1]: string(10) "2012-09-06"
          [2]: string(10) "2012-09-08"
          [3]: string(10) "2012-09-10"
        }

I want to check if the first element from Array A equals the first element from Array B, if it does then write second element (in this case 1) from array A to an new Array C (one dimensional) else don’t write anything in an array C and next check if element with index 2 from an array A equals second element [1]: string(10) "2012-09-06" from an array B if so the write fourth element ([3]: int 1) from an array A to an array C etc. so an array C would have int elements only.
If someone could help me out how to sort this out please I would be very happy

Answer 1

If you really need to do it this way, you could do something like the following:

foreach($arrayB as $bRow)
{
    if(FALSE !== ($key = array_search($bRow, $arrayA))
    {
        $arrayC[] = $arrayA[$key+1];
    }
}

However, a string-indexed array would probably be better for Array A. Use the following for the 3 examples below:

$arrayA = array("2012-08-01" => 1, "2012-08-03" => 1, "2012-08-07" => 2, "2012-08-09" => 2, "2012-08-27" => 1);
$arrayB = array("2012-09-04", "2012-09-06", "2012-09-08", "2012-09-10");
$arrayC = array();

If Array A always contains more elements than Array B (or the same number):

foreach($arrayA as $key=>$value)
{
    if(in_array($key, $arrayB))
    {
        $arrayC[] = $value;
    }
}

If Array B always contains more elements than Array A (or the same number):

foreach($arrayB as $bRow)
{
    if(isset($arrayA[$bRow]))
    {
        $arrayC[] = $arrayA[$bRow];
    }
}

If it is possible that sometimes Array A is longer and sometimes Array B is longer:

$matchedIndexes = array();

foreach($arrayA as $key=>$value)
{
    if(in_array($key, $arrayB))
    {
        $arrayC[] = $value;
        $matchedIndexes[] = $key;
    }
}

foreach($arrayB as $bRow)
{
    // Only add the entries that we did not already add when looping through $arrayA
    if(!in_array($key, $matchedIndexes) && isset($arrayA[$bRow]))
    {
        $arrayC[] = $arrayA[$bRow];
    }
}

Populating arrayC with zeros foreach entry in arrayA that does not have a match in arrayB:

foreach($arrayA as $key=>$value)
{
    if(in_array($key, $arrayB))
    {
        $arrayC[] = $value;
    }
    else
    {
        $arrayC[] = 0;
    }
}