When you need to measure edit distance by grapheme clusters, 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.
grapheme_levenshtein provides the behavior described below. A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
What Is grapheme_levenshtein in PHP?
Measure edit distance by grapheme clusters. A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
Its syntax is:
grapheme_levenshtein(...)
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: Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization. This function was introduced in PHP 8.5 and is unavailable in PHP 8.4.
Example 1: Basic Usage
This first example demonstrates how to measure edit distance by grapheme clusters with a small input.
<?php
echo grapheme_levenshtein("café", "cafe");
The example uses the simplest useful form. A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point. 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. Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization.
<?php
echo grapheme_levenshtein("cat", "cut");
Compare the result to the first example. Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters.
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 8.5 or newer is also required.
<?php
$enteredWord = "Résumé";
$expectedWord = "Resume";
echo grapheme_levenshtein($enteredWord, $expectedWord);
The example keeps the operation visible and gives you a starting point for using it in an application. Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization.
Important Behavior and Edge Cases
- Core behavior: A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
- Return value: Check the result separately from changes to passed-in arrays, iterators, or object state.
- Data constraints: Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization.
- Environment: The intl extension is required for this example. PHP 8.5 or newer is also required.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
grapheme_levenshtein | Measure edit distance by grapheme clusters. |
| Related PHP APIs | Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Assuming the function works on every kind of input | Follow the declared argument types and check the input format before calling it. |
| Ignoring the behavior of the result | Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization. |
| Using the wrong related PHP API | Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters. |
Key Takeaways
grapheme_levenshteinhelps you measure edit distance by grapheme clusters.- A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
- Only available beginning with PHP 8.5; the function does not itself implement locale-aware equivalence or normalization.
- Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters.
grapheme_levenshtein is useful when you need to measure edit distance by grapheme clusters. Start with the small examples, then adapt the practical example while respecting its input and environment requirements.