Multi-Dimensional Arrays

There are times when you will want to include arrays within your array or represent something more two-dimensional than a simple list of data. Fortunately, PHP supports this functionality with easy-to-use multi-dimensional arrays.

Since the value of an array element can be anything, it can also be another array. This is how multi-dimensional arrays are created.

<?php

  $bikes = array();
  $bikes["Tourmeister"] = array("name" => "Grande Tour Meister",
                                "engine_cc" => 1100,
                                "price" =>12999);
  $bikes["Slasher1000"] = array("name" => "Slasher XYZ 1000",
                                "engine_cc" => 998,
                                "price" => 11450);
  $bikes["OffRoadster"] = array("name" => "Off-Roadster",
                                "engine_cc" => 550,
                                "price" => "4295");

?>

You can access the elements in a multi-dimensional array by putting pairs of square brackets next to each other in code:

<?php

  $names = array_keys($bikes);

  foreach ($names as $name)
  {
    print $bikes[$name] . " costs: " . $bikes[$name]["price"]
          . "<br/>\n";
  }

?>

Another helpful way to create multi-dimensional arrays would be to use the array_fill method. This creates an array for you where all the (integer-keyed) values have the same initial value. If we wanted to create a 3x3 matrix, we could use array_fill method, which takes three arguments: the starting index to use, the number of elements to create, and the value to put in each element. By having this value returned by array_fill, we can quickly create a two-dimensional array full of them:

<?php

   $threex3matrix = array_fill(0, 3, array_fill(0, 3, 1));

   foreach($threex3matrix as $row)
   {
     echo "{$row[0]} {$row[1]} {$row[2]}<br/>\n";
   }
?>

The output would be

1 1 1
1 1 1
1 1 1

The count method can optionally be given one more parameter, COUNT_RECURSIVE, which is how we count all of the elements in multi-dimensional arrays. This parameter value tells the function to count the number of values in the arrays contained within the counted array.

<?php

  $colors = array("non-colors" => array("white", "black"),
                   "primary" => array("blue", "yellow", "red"),
                   "happy" => array("pink", "orange"));
  $elems = count($colors, COUNT_RECURSIVE);

  //
  // The following prints out 10 (3 top-level items in
  // $colors containing a total of 7 sub-items)
  //
  echo "\$colors has a total of $elems elements<br/>\n";

?>

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