When you need to extract a substring by grapheme boundaries, 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_substr 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_substr in PHP?
Extract a substring by grapheme boundaries. A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
Its syntax is:
grapheme_substr(...)
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: Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start.
Example 1: Basic Usage
This first example demonstrates how to extract a substring by grapheme boundaries with a small input.
<?php
echo grapheme_substr("café", 0, 3);
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. Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start.
<?php
echo grapheme_substr("A🙂B", 1, 1);
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
$headline = "Hello 👋 World";
$preview = grapheme_substr($headline, 0, 7);
echo $preview;
The example keeps the operation visible and gives you a starting point for using it in an application. Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start.
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: Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start.
- Environment: The intl extension is required for this example.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
grapheme_substr | Extract a substring by grapheme boundaries. |
| 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 | Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start. |
| Using the wrong related PHP API | Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters. |
Key Takeaways
grapheme_substrhelps you extract a substring by grapheme boundaries.- A grapheme cluster is a user-perceived character, potentially consisting of more than one Unicode code point.
- Use grapheme offsets, not byte offsets; see grapheme_extract() for extraction with a byte start.
- Use strlen() for bytes, mb_* for code points and grapheme_* for grapheme clusters.
grapheme_substr is useful when you need to extract a substring by grapheme boundaries. Start with the small examples, then adapt the practical example while respecting its input and environment requirements.