How do I Sort a Multidimensional Array in PHP

You can use array_multisort()

Try something like this:

foreach ($mdarray as $key => $row) {
    // replace 0 with the field's index/key
    $dates[$key]  = $row[0];
}

array_multisort($dates, SORT_DESC, $mdarray);

For PHP >= 5.5.0 just extract the column to sort by. No need for the loop:

array_multisort(array_column($mdarray, 0), SORT_DESC, $mdarray);

With usort. Here's a generic solution, that you can use for different columns:

class TableSorter {
  protected $column;
  function __construct($column) {
    $this->column = $column;
  }
  function sort($table) {
    usort($table, array($this, 'compare'));
    return $table;
  }
  function compare($a, $b) {
    if ($a[$this->column] == $b[$this->column]) {
      return 0;
    }
    return ($a[$this->column] < $b[$this->column]) ? -1 : 1;
  }
}

To sort by first column:

$sorter = new TableSorter(0); // sort by first column
$mdarray = $sorter->sort($mdarray);

Multiple row sorting using a closure

Here's another approach using uasort() and an anonymous callback function (closure). I've used that function regularly. PHP 5.3 required – no more dependencies!

/**
 * Sorting array of associative arrays - multiple row sorting using a closure.
 * See also: http://the-art-of-web.com/php/sortarray/
 *
 * @param array $data input-array
 * @param string|array $fields array-keys
 * @license Public Domain
 * @return array
 */
function sortArray( $data, $field ) {
    $field = (array) $field;
    uasort( $data, function($a, $b) use($field) {
        $retval = 0;
        foreach( $field as $fieldname ) {
            if( $retval == 0 ) $retval = strnatcmp( $a[$fieldname], $b[$fieldname] );
        }
        return $retval;
    } );
    return $data;
}

/* example */
$data = array(
    array( "firstname" => "Mary", "lastname" => "Johnson", "age" => 25 ),
    array( "firstname" => "Amanda", "lastname" => "Miller", "age" => 18 ),
    array( "firstname" => "James", "lastname" => "Brown", "age" => 31 ),
    array( "firstname" => "Patricia", "lastname" => "Williams", "age" => 7 ),
    array( "firstname" => "Michael", "lastname" => "Davis", "age" => 43 ),
    array( "firstname" => "Sarah", "lastname" => "Miller", "age" => 24 ),
    array( "firstname" => "Patrick", "lastname" => "Miller", "age" => 27 )
);

$data = sortArray( $data, 'age' );
$data = sortArray( $data, array( 'lastname', 'firstname' ) );

Here is a php4/php5 class that will sort one or more fields:

// a sorter class
//  php4 and php5 compatible
class Sorter {

  var $sort_fields;
  var $backwards = false;
  var $numeric = false;

  function sort() {
    $args = func_get_args();
    $array = $args[0];
    if (!$array) return array();
    $this->sort_fields = array_slice($args, 1);
    if (!$this->sort_fields) return $array();

    if ($this->numeric) {
      usort($array, array($this, 'numericCompare'));
    } else {
      usort($array, array($this, 'stringCompare'));
    }
    return $array;
  }

  function numericCompare($a, $b) {
    foreach($this->sort_fields as $sort_field) {
      if ($a[$sort_field] == $b[$sort_field]) {
        continue;
      }
      return ($a[$sort_field] < $b[$sort_field]) ? ($this->backwards ? 1 : -1) : ($this->backwards ? -1 : 1);
    }
    return 0;
  }

  function stringCompare($a, $b) {
    foreach($this->sort_fields as $sort_field) {
      $cmp_result = strcasecmp($a[$sort_field], $b[$sort_field]);
      if ($cmp_result == 0) continue;

      return ($this->backwards ? -$cmp_result : $cmp_result);
    }
    return 0;
  }
}

/////////////////////
// usage examples

// some starting data
$start_data = array(
  array('first_name' => 'John', 'last_name' => 'Smith', 'age' => 10),
  array('first_name' => 'Joe', 'last_name' => 'Smith', 'age' => 11),
  array('first_name' => 'Jake', 'last_name' => 'Xample', 'age' => 9),
);

// sort by last_name, then first_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'last_name', 'first_name'));

// sort by first_name, then last_name
$sorter = new Sorter();
print_r($sorter->sort($start_data, 'first_name', 'last_name'));

// sort by last_name, then first_name (backwards)
$sorter = new Sorter();
$sorter->backwards = true;
print_r($sorter->sort($start_data, 'last_name', 'first_name'));

// sort numerically by age
$sorter = new Sorter();
$sorter->numeric = true;
print_r($sorter->sort($start_data, 'age'));

The "Usort" function is your answer.
http://php.net/usort

Before I could get the TableSorter class to run I had came up with a function based on what Shinhan had provided.

function sort2d_bycolumn($array, $column, $method, $has_header)
  {
  if ($has_header)  $header = array_shift($array);
  foreach ($array as $key => $row) {
    $narray[$key]  = $row[$column]; 
    }
  array_multisort($narray, $method, $array);
  if ($has_header) array_unshift($array, $header);
  return $array;
  }

• $array is the MD Array you want to sort.
• $column is the column you wish to sort by.
• $method is how you want the sort performed, such as SORT_DESC
• $has_header is set to true if the first row contains header values that you don't want sorted.

I prefer to use array_multisort. See the documentation here.