The sort() Function in PHP

The sort() function in PHP is used to sort arrays in ascending order. It rearranges the elements of an array from lowest to highest values.

Syntax

sort(array &$array, int $flags = SORT_REGULAR): bool

Parameters

• $array (required): The input array to be sorted (passed by reference)
• $flags (optional): Specifies how to compare items. Possible values:
  • SORT_REGULAR - Compare items normally (don't change types)
  • SORT_NUMERIC - Compare items numerically
  • SORT_STRING - Compare items as strings
  • SORT_LOCALE_STRING - Compare items as strings based on current locale
  • SORT_NATURAL - Compare items as strings using natural ordering
  • SORT_FLAG_CASE - Can be combined with SORT_STRING or SORT_NATURAL for case-insensitive sorting

Return Value

• Returns true on success
• Returns false on failure

Examples

1. Basic Sorting of Numeric Arrays

<?php
$numbers = [4, 2, 8, 6, 1];
sort($numbers);

print_r($numbers);
// Output: Array ( [0] => 1 [1] => 2 [2] => 4 [3] => 6 [4] => 8 )
?>

2. Sorting String Arrays

<?php
$fruits = ["banana", "apple", "cherry", "date"];
sort($fruits);

print_r($fruits);
// Output: Array ( [0] => apple [1] => banana [2] => cherry [3] => date )
?>

3. Sorting with Different Flags

<?php
$mixed = ["10", "2", "100", "25"];

// Regular sorting (as strings)
sort($mixed, SORT_REGULAR);
print_r($mixed); 
// Output: Array ( [0] => 10 [1] => 100 [2] => 2 [3] => 25 )

// Numeric sorting
sort($mixed, SORT_NUMERIC);
print_r($mixed);
// Output: Array ( [0] => 2 [1] => 10 [2] => 25 [3] => 100 )
?>

4. Case-Insensitive Sorting

<?php
$words = ["Apple", "banana", "Cherry", "date"];

// Case-sensitive (default)
sort($words);
print_r($words);
// Output: Array ( [0] => Apple [1] => Cherry [2] => banana [3] => date )

// Case-insensitive
sort($words, SORT_STRING | SORT_FLAG_CASE);
print_r($words);
// Output: Array ( [0] => Apple [1] => banana [2] => Cherry [3] => date )
?>

5. Natural Order Sorting

<?php
$files = ["file1.txt", "file10.txt", "file2.txt", "file20.txt"];

// Regular string sorting
sort($files);
print_r($files);
// Output: Array ( [0] => file1.txt [1] => file10.txt [2] => file2.txt [3] => file20.txt )

// Natural order sorting
sort($files, SORT_NATURAL);
print_r($files);
// Output: Array ( [0] => file1.txt [1] => file2.txt [2] => file10.txt [3] => file20.txt )
?>

6. Important Note: Index Reassignment

<?php
$associative = [
    "b" => "banana",
    "a" => "apple",
    "c" => "cherry"
];

echo "Before sorting (associative array):\n";
print_r($associative);
// Output: Array ( [b] => banana [a] => apple [c] => cherry )

sort($associative);
echo "After sort() - keys are lost and reassigned:\n";
print_r($associative);
// Output: Array ( [0] => apple [1] => banana [2] => cherry )
?>

Important Characteristics

1. Modifies Original Array

<?php
$original = [3, 1, 2];
sort($original);
// $original is now [1, 2, 3]
?>

2. Key Reassignment

<?php
$array = [10 => "ten", 5 => "five", 20 => "twenty"];
sort($array);
// Keys are reset to 0, 1, 2: [0 => "five", 1 => "ten", 2 => "twenty"]
?>

3. Return Value Usage

<?php
$array = [3, 1, 2];
if (sort($array)) {
    echo "Array sorted successfully!";
} else {
    echo "Sorting failed!";
}
?>

Related Sorting Functions

Practical Example: Sorting User Data

<?php
$users = [
    ["name" => "John", "age" => 25],
    ["name" => "Alice", "age" => 30],
    ["name" => "Bob", "age" => 22]
];

// Extract ages for sorting
$ages = array_column($users, 'age');
sort($ages);

echo "Ages in ascending order:\n";
print_r($ages);
// Output: Array ( [0] => 22 [1] => 25 [2] => 30 )
?>

Best Practices

1. Use appropriate flags for the data type you're sorting
2. Be aware that keys are reassigned - use asort() if you need to preserve keys
3. For associative arrays, consider using asort() or ksort() instead
4. For complex sorting, use usort() with a custom comparison function

The sort() function is efficient and perfect for simple sorting tasks where you don't need to preserve the original array keys.