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How do I sort arrays in PHP using functions like sort(), asort(), ksort(), rsort()?
How do I sort arrays in PHP using functions like sort(), asort(), ksort(), rsort()?
Jun 27, 2025 am 02:10 AM
PHP provides several functions for sorting arrays. 1. sort() sorts numeric-indexed arrays in ascending order and reindexes them. 2. rsort() does the same but in descending order. 3. asort() sorts associative arrays by value while preserving key-value associations. 4. ksort() sorts associative arrays by key while keeping values intact. Each function modifies the original array directly and is suited for specific use cases such as data organization or display.
Sorting arrays in PHP can be done with several built-in functions depending on what exactly you're trying to achieve. The main ones are sort(), asort(), ksort(), and rsort(). Each behaves differently, especially when it comes to whether they preserve keys or sort by value or key.
Sorting numerically indexed arrays with sort()
If you have a simple array with numeric indexes and you just want the values sorted in ascending order, sort() is your go-to function. It reindexes the array numerically after sorting.
Example:
$numbers = [3, 1, 4, 2]; sort($numbers); // Result: [1, 2, 3, 4]
- This function modifies the original array — no need to assign it to a new variable.
- If you need descending order, this isn't the right tool. You’ll want
rsort()for that instead. - It's commonly used for cleaning up numeric data before display or processing.
Keeping key-value associations with asort()
When working with associative arrays (arrays where keys matter), use asort() if you want to sort by value but keep the keys attached. This is useful when you're dealing with things like user scores or product prices and want to maintain which value belongs to which key.
Example:
$scores = ['Alice' => 85, 'Bob' => 90, 'Clare' => 80]; asort($scores); // Result: ['Clare' => 80, 'Alice' => 85, 'Bob' => 90]
- The keys stay tied to their values after sorting.
- Values are still sorted in ascending order by default.
- Like
sort(), this changes the original array directly.
Sorting by key with ksort()
If your array's keys are meaningful and you want them in order (like dates, letters, or custom IDs), ksort() will sort the array based on the keys while keeping their corresponding values intact.
Example:
$data = ['z-product' => 10, 'a-product' => 25, 'm-product' => 5]; ksort($data); // Result: ['a-product' => 25, 'm-product' => 5, 'z-product' => 10]
- Keys are sorted in ascending order by default.
- Very helpful when outputting data in a specific key-based sequence, like alphabetically listing items by name.
- Again, this alters the original array.
Reverse sorting with rsort()
If you want values sorted from highest to lowest (descending order) and don’t care about preserving keys, use rsort(). It’s essentially the reverse version of sort().
Example:
$values = [10, 30, 20]; rsort($values); // Result: [30, 20, 10]
- Works only on numerically indexed arrays.
- Often used for quick ranking or filtering top results.
- Just like
sort(), it reindexes the array.
So depending on your needs:
- Use
sort()for basic ascending numeric-indexed sorting - Use
rsort()for descending numeric-indexed sorting - Use
asort()to sort associative arrays by value - Use
ksort()to sort associative arrays by key
基本上就這些。
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