PHP developers sometimes need to sort an array by keys using a custom comparator. This comes up when preparing data, displaying results, or integrating information with other services.
The uksort() operation handles this particular task. The following examples show its result, its limitations, and a practical way to apply it.
What Is uksort() in PHP?
Sort an array by keys using a custom comparator.
Its syntax is:
uksort(array &$array, callable $callback): true
The syntax shows the expected parameters and return type. Arguments marked with an ampersand are passed by reference and may be modified. Optional parameters control additional behavior; values must match the declared types.
Important: Values stay paired with their keys. Comparator results must consistently indicate order.
Parameters:
&$array— May be updated by the function.$callback— A named input or configuration argument; use the declared type and optional default shown above.
Example 1: Basic Usage
This first example uses a small input to demonstrate the main result of uksort().
<?php
$data = ["b" => 2, "A" => 1]; uksort($data, "strcasecmp"); print_r($data);
Output:
Array
(
[A] => 1
[b] => 2
)
The output demonstrates the primary operation: sort an array by keys using a custom comparator.
Example 2: Understanding Another Case
This second example changes the input or option to reveal a different behavior of uksort().
<?php
$items = ["item20" => "B", "item3" => "A"]; uksort($items, "strnatcmp"); print_r($items);
Output:
Array
(
[item3] => A
[item20] => B
)
Compared with the first example, this one illustrates the same operation with a different input shape or option. Values stay paired with their keys. Comparator results must consistently indicate order.
Practical Example: A Real Application Scenario
Here is a practical use of uksort() with realistic sample information. Adapt the values to match your application.
<?php
$headers = ["x-Region" => "EU", "Accept" => "json", "content-type" => "text"]; uksort($headers, "strcasecmp"); foreach ($headers as $name => $value) { echo "$name: $value\n"; }
Output:
Accept: json
content-type: text
x-Region: EU
This is a useful starting point, but production code should check errors and validate values before performing the operation. Values stay paired with their keys. Comparator results must consistently indicate order.
Important Behavior and Edge Cases
Values stay paired with their keys. Comparator results must consistently indicate order.
- Input: Use the expected PHP types and validate user-provided values.
- Result: Check the return value separately from any modifications to the input.
- Environment: For extension, database, or filesystem examples, verify availability and handle failures before accessing results.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
uksort() | Sort an array by keys using a custom comparator. |
| Related functions | ksort() uses predefined sort flags; uasort() sorts by values instead. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Expecting a sorted copy without changing the input | These sort functions modify the array directly; copy it first if you need the original. |
| Using the wrong sort target | Decide whether to sort keys or values, and whether key associations must remain intact. |
| Assuming every comparison handles text in the same way | ksort() uses predefined sort flags; uasort() sorts by values instead. |
Key Takeaways
uksort()lets you sort an array by keys using a custom comparator.- Values stay paired with their keys. Comparator results must consistently indicate order.
- ksort() uses predefined sort flags; uasort() sorts by values instead.
- Check input, return values, and environmental requirements when adapting the examples.
uksort() provides a focused PHP operation for sort an array by keys using a custom comparator. Start with the simple examples, then adapt the practical example with the correct checks for your project.