John Davidson

Message:

This question is intended as a reference for questions about sorting arrays in PHP. It is easy to think that your particular case is unique and worthy of a new question, but most are actually minor variations of one of the solutions on this page.

If your question is closed as a duplicate of this one, please ask for your question to be reopened only if you can explain why it differs markedly from all of the below.

How do I sort an array in PHP?

How do I sort a complex array in PHP?

How do I sort an array of objects in PHP?

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1. Basic one-dimensional arrays; Incl. Multidimensional arrays, incl. arrays of objects; Incl. Sorting one array based on another

   
   



2. Sorting with SPL

   
   



3. Stable sort

   
   

For the practical answer using PHP's existing functions see 1., for the academic in-detail answer on sorting algorithms (which PHP's functions implement and which you may need for really, really complex cases), see 2.

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My Answer:
1. Sorting arrays in PHP:

To sort a basic one-dimensional array in PHP, you can use the `sort()`, `rsort()`, `asort()`, `arsort()`, `ksort()`, and `krsort()` functions. These functions sort the array in different ways:

- `sort()`: Sorts an array in ascending order
- `rsort()`: Sorts an array in descending order
- `asort()`: Sorts an associative array in ascending order, maintaining key-value pairs
- `arsort()`: Sorts an associative array in descending order, maintaining key-value pairs
- `ksort()`: Sorts an associative array by keys in ascending order
- `krsort()`: Sorts an associative array by keys in descending order

Example:
php
$array = [3, 1, 2];
sort($array);
print_r($array); // Output: [1, 2, 3]


For sorting multidimensional arrays or arrays of objects, you can use the `usort()` function with a custom comparison function. This allows you to define how the elements should be compared for sorting.

Example:
php
$users = [
['name' => 'John', 'age' => 30],
['name' => 'Jane', 'age' => 25],
['name' => 'Alice', 'age' => 35]
];

usort($users, function($a, $b) {
return $a['age'] - $b['age'];
});

print_r($users);


2. Sorting with SPL:

PHP's Standard PHP Library (SPL) provides additional sorting functionality through classes like `ArrayObject` and `SplHeap`. These classes offer more advanced sorting options and can be useful for complex sorting requirements.

Example using `ArrayObject`:
php
$array = new ArrayObject([3, 1, 2]);
$array->asort();
print_r($array->getArrayCopy());


3. Stable sort:

PHP's sorting functions are stable, meaning that the original order of equal elements is preserved after sorting. This can be important when sorting arrays based on multiple criteria.

Example:
php
$users = [
['name' => 'John', 'age' => 30],
['name' => 'Jane', 'age' => 25],
['name' => 'Alice', 'age' => 30]
];

usort($users, function($a, $b) {
return $a['age'] - $b['age'];
});

print_r($users);


These are some of the common ways to sort arrays and data in PHP. Depending on your specific requirements, you may need to use a combination of these methods or create custom sorting functions.