PHP Collator::compare() Method: Usage and Examples

When you need to compare two localized strings, it helps to understand both the normal result and what changes with different inputs. This guide focuses on practical examples rather than repeating PHP background material.

Collator::compare provides the behavior described below. A Collator applies locale-dependent ICU collation rules rather than byte-by-byte ordering.

What Is Collator::compare in PHP?

Compare two localized strings. A Collator applies locale-dependent ICU collation rules rather than byte-by-byte ordering.

Its syntax is:

$collator->compare(...)

Parameters and return value: Read the argument names and optional values in the signature above. Methods use an existing object, while stand-alone functions take direct arguments. The examples demonstrate the relevant arguments and the value returned or the object modified.

Important: A comparison result is negative, zero, or positive; collation depends on the selected locale and strength.

Example 1: Basic Usage

This first example demonstrates how to compare two localized strings with a small input.

<?php

$collator = new Collator("de_DE");
$words = ["zebra", "äpfel", "apfel"];
$comparison = $collator->compare("äpfel", "zebra");
var_dump($comparison);

The example uses the simplest useful form. A Collator applies locale-dependent ICU collation rules rather than byte-by-byte ordering. The output may depend on the active ICU locale, PHP configuration, or input supplied to the function.

Example 2: Another Case

Here the input or option changes, making it easier to see where the behavior differs. A comparison result is negative, zero, or positive; collation depends on the selected locale and strength.

<?php

$collator = new Collator("de_DE");
$words = ["zebra", "äpfel", "apfel"];
$comparison = $collator->compare("café", "cafe");
var_dump($comparison);

Compare the result to the first example. strcmp() compares bytes; Collator::compare() and Collator sorting methods use locale collation.

Practical Example: Applying the Function

This standalone example shows how the same operation fits into a small application task. The intl extension is required for this example.

<?php

$collator = new Collator("de_DE");
$words = ["zebra", "äpfel", "apfel"];
$words = ["zebra", "äpfel", "apfel"];
usort($words, fn($firstWord, $secondWord) => $collator->compare($firstWord, $secondWord));
print_r($words);

The example keeps the operation visible and gives you a starting point for using it in an application. A comparison result is negative, zero, or positive; collation depends on the selected locale and strength.

Important Behavior and Edge Cases

• Core behavior: A Collator applies locale-dependent ICU collation rules rather than byte-by-byte ordering.
• Return value: Check the result separately from changes to passed-in arrays, iterators, or object state.
• Data constraints: A comparison result is negative, zero, or positive; collation depends on the selected locale and strength.
• Environment: The intl extension is required for this example.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Collator::compare helps you compare two localized strings.
• A Collator applies locale-dependent ICU collation rules rather than byte-by-byte ordering.
• A comparison result is negative, zero, or positive; collation depends on the selected locale and strength.
• strcmp() compares bytes; Collator::compare() and Collator sorting methods use locale collation.

Collator::compare is useful when you need to compare two localized strings. Start with the small examples, then adapt the practical example while respecting its input and environment requirements.