PHP Function to Extract Parts of a Multi-Dimensional Array Based Upon Variable Criteria

Question

Given a multi-dimensional array, I'm looking for a method that will extract various parts of that array, given variable (i.e., different) criteria.

For example, if this is my data:

array(
  '0' => array(
        '0' => 'aaaaaa',
        '1' => 'bbbbb',
        '2' => 'ccccc'
  ), 
  '1' => array(
        '0' => 'aa2ssa',
        '1' => 'bb3242bb,
        '2' => 'ccccc234'
  ),
  '2' => array(
        '0' => 'aaa234aa',
        '1' => 'b3242b',
        '2' => 'cewrcc'
  ),
      (etc)
)

I want to be able to call a function

function new_array( index, sub_index )      

that returns an array based upon the index and sub_index parameters. Using the same data but different parameters would return different data.

Example 1

new_array( array(0, 2), ( array(1, 2), array(0, 2) ) )

Expected results:

array(
  '0' => array(
        '1' => 'bbbbb',
        '2' => 'ccccc'
  ), 
  '2' => array(
        '0' => 'aaa234aa',
        '2' => 'cewrcc'
  )
)

Example 2

new_array( array(2), ( array(0, 2) ) )

Expected results:

array(
  '2' => array(
        '0' =>'aaa234aa',
        '1' => 'b3242b'
  )
)

Anybody know how to do this? Thank you!

Answer 1

An alternate solution to @Orbling's is this:

function populateData() // CHANGE ME to populate the info how you please
{
  $seed = 'abcdefghijklmnopqrstuvwxyz0123456789';
  $_ = ''; $length = rand(5,8);
  for ($__ = 0; $__ < $length; $__++) $_ .= substr($seed,rand(0,strlen($seed)),1);
  return $_;
}

function new_array()
{
  $args = func_num_args();
  if ($args == 0)
    return FALSE; // flag error if no arguments are passed

  $template = func_get_arg(0);
  if ($template == null || !is_array($template) || $args < (count($template)+1))
    return FALSE; // flag error if we don't have enough information

  $resultAry = Array();
  $arg = 1;
  foreach ($template as $t)
  {
    $resultArySub = Array();

    $templateSub = func_get_arg($arg++);
    if ($templateSub == FALSE || !is_array($templateSub)) 
      return FALSE; // error checking for valid input

    foreach ($templateSub as $tS)
      $resultArySub[$tS] = populateData();

    $resultAry[$t] = $resultArySub;
  }
  return $resultAry;
}

header('Content-Type: text/plain');
echo "your request (or so i understood):\r\n";
$test = new_array(array(0,2),array(1,2),array(0,2));
var_dump($test);

echo "\r\nextra array on end is ignored:\r\n";
$test = new_array(array(4,2),array(1,2),array(0,2),array(3,5));
var_dump($test);

echo "\r\nno data is a FALSE:\r\n";
$test = new_array();
var_dump($test);

echo "\r\ntoo few arguments for what was supplied in first argument is a FALSE:\r\n";
$test = new_array(array(1,2,3),array(4,5),array(6,7));
var_dump($test);

echo "\r\nas long as there's as \"array argument\" for every element of the \"first argument\", this will work:\r\n";
$test = new_array(array(1,2,3,4,5,6,7),array(1),array(2),array(3),array(4),array(5),array(6),array(7));
var_dump($test);

echo "\r\nall arguments must be an array\r\n";
$test = new_array(array(1,2),'not','arrays');
var_dump($test);

Results in an array with random entries. The outcome of the above would be:

your request (or so i understood):
array(2) {
  [0]=>
  array(2) {
    [1]=>
    string(8) "mjdfsmda"
    [2]=>
    string(8) "qg2bzsj6"
  }
  [2]=>
  array(2) {
    [0]=>
    string(7) "345plm8"
    [2]=>
    string(7) "1exlla6"
  }
}

extra array on end is ignored:
array(2) {
  [4]=>
  array(2) {
    [1]=>
    string(5) "0ngei"
    [2]=>
    string(5) "q6tmg"
  }
  [2]=>
  array(2) {
    [0]=>
    string(7) "4enz61q"
    [2]=>
    string(6) "6bojtn"
  }
}

no data is a FALSE:
bool(false)

too few arguments for what was supplied in first argument is a FALSE:
bool(false)

as long as there's as "array argument" for every element of the "first argument", this will work:
array(7) {
  [1]=>
  array(1) {
    [1]=>
    string(7) "ndulmi9"
  }
  [2]=>
  array(1) {
    [2]=>
    string(7) "jip402j"
  }
  [3]=>
  array(1) {
    [3]=>
    string(5) "3bn0d"
  }
  [4]=>
  array(1) {
    [4]=>
    string(8) "b80le1jh"
  }
  [5]=>
  array(1) {
    [5]=>
    string(5) "x31sw"
  }
  [6]=>
  array(1) {
    [6]=>
    string(8) "x8e3dge7"
  }
  [7]=>
  array(1) {
    [7]=>
    string(8) "vcpf997y"
  }
}

all arguments must be an array
bool(false)

Answer 2

Assuming that you wish the function to process an existing array and filter out the data, as seems to be the case then you could do this:

function new_array($original, $topKeys, $subKeys) {
    if (count($topKeys) != count($subKeys)) {
        return $original;
    }

    $newArray = array();
    foreach ($topKeys as $cTopKey) {
        $cSubKeys = array_shift($subKeys);

        if (array_key_exists($cTopKey, $original)) {
            $newArray[$cTopKey] = array();
            foreach ($cSubKeys as $cSubKey) {
                if (array_key_exists($cSubKey, $original[$cTopKey])) {
                    $newArray[$cTopKey][$cSubKey] = $original[$cTopKey][$cSubKey];
                }
            }
        }
    }

    return $newArray;
}

If you have PHP v5.1+ and the indexes are guaranteed to be available, and in order, then I believe you can do it more simply:

function new_array($original, $topKeys, $subKeys) {
    $newArray = array_intersect_key($original, array_flip($topKeys));
    foreach ($newArray as $cKey => $cSub) {
        $cSubKeys = array_shift($subKeys);
        $newArray[$cKey] = array_intersect_key($cSub, $cSubKeys);
    }

    return $newArray;
}

The danger in that is I do not know if array_intersect_key() is defined to keep the original ordering of elements. If not, then further code would need to be added to match the sub keys with the original, ideally the subkeys would be sub arrays of the first parameter anyhow.

Answer 3

why not just

$a = array('0' => 
               array('1' => 'bbbb', 
                     '2' => 'ccccc'), 
           '2' => 
               array('0' => 'aaaa', 
                     '2' => 'cewrcc')
           );

Why use a function to do the same?