How to Efficiently Sort a Multidimensional PHP Array by Column, Including Dates and Custom Criteria?

Sorting a Multidimensional Array in PHP: A Flexible Approach

The Query

How do you efficiently arrange a multidimensional array based on a specified column, particularly when the data includes dates and you desire customized sorting criteria?

The Answer

Introducing an Enhanced Solution for PHP 5.3

This solution offers several advantages:

• Reusable: Define the sort column as a variable.
• Flexible: Handle multiple sort columns and secondary tiebreakers.
• Reversible: Sort in either ascending or descending order for each column.
• Extensible: Utilize custom projections for complex or non-comparable data.
• Associative: Use usort or uasort for compatibility with associative arrays.

The Code

function make_comparer() {
    // Normalize criteria
    $criteria = func_get_args();
    foreach ($criteria as $index => $criterion) {
        $criteria[$index] = is_array($criterion) ? array_pad($criterion, 3, null) : array($criterion, SORT_ASC, null);
    }

    return function ($first, $second) use (&$criteria) {
        foreach ($criteria as $criterion) {
            // Comparison details
            list($column, $sortOrder, $projection) = $criterion;
            $sortOrder = $sortOrder === SORT_DESC ? -1 : 1;

            // Project and compare values
            $lhs = $projection ? call_user_func($projection, $first[$column]) : $first[$column];
            $rhs = $projection ? call_user_func($projection, $second[$column]) : $second[$column];

            // Determine the comparison result
            if ($lhs < $rhs) {
                return -1 * $sortOrder;
            } elseif ($lhs > $rhs) {
                return 1 * $sortOrder;
            }
        }

        // Tiebreakers exhausted
        return 0;
    };
}

Usage

Consider the sample data:

$data = array(
    array('zz', 'name' => 'Jack', 'number' => 22, 'birthday' => '12/03/1980'),
    array('xx', 'name' => 'Adam', 'number' => 16, 'birthday' => '01/12/1979'),
    array('aa', 'name' => 'Paul', 'number' => 16, 'birthday' => '03/11/1987'),
    array('cc', 'name' => 'Helen', 'number' => 44, 'birthday' => '24/06/1967'),
);

Basic Sorting:

• Sort by the "name" column: usort($data, make_comparer('name'));

Sorting with Multiple Columns:

• Sort by the "number" column and then by the zero-indexed column: usort($data, make_comparer('number', 0));

Advanced Features:

• Reverse Sorting: Sort by the "name" column descending: usort($data, make_comparer(['name', SORT_DESC]));
• Custom Projections: Project birthday dates to timestamps for sorting: usort($data, make_comparer(['birthday', SORT_ASC, 'date_create']));

Complex Use Case:

• Sort by the "number" column descending, followed by the projected "birthday" column ascending:

  usort($data, make_comparer(
    ['number', SORT_DESC],
    ['birthday', SORT_ASC, 'date_create']
  ));

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