[PHP-NOTES] note 130380 added to function.mb-substr-count

Should I use multibyte version of substr_count php function, when my needle is space?

ChatGPT said:

When deciding whether to use the multibyte version of substr_count() (i.e., mb_substr_count()) in PHP, even when your needle is a space character (' '), the answer depends on the encoding of your string.

Key Considerations

1. The needle is a single-byte character (' ').

— The space character (' ') is a single-byte ASCII character, even in multibyte encodings like UTF-8.
— So, if your string is guaranteed to be plain ASCII or the space character is what you're counting, substr_count() will work fine even with multibyte strings.

2. The haystack may contain multibyte characters (e.g., UTF-8 text with non-ASCII characters like ü, ñ, 漢).

— substr_count() doesn't interpret multibyte sequences correctly as characters, but it doesn't matter for simple counting of a byte sequence like space.
— The only risk would be if the byte 0x20 (space) appears inside a multibyte sequence—but in UTF-8, that doesn't happen.

Conclusion

✅ Use substr_count() for counting spaces, even in multibyte strings like UTF-8.

🔀 Use mb_substr_count() if:

— You're working in multibyte encodings other than UTF-8.
— Your needle itself is a multibyte character (e.g., é, 漢).
— You're dealing with character boundaries explicitly and want strict multibyte safety.

Example:
<?php

$str = "你好 世界 こんにちは 세계 안녕 hello world";
$count = substr_count($str, ' '); // This will work fine for counting spaces
echo $count;

?>
In this case, substr_count() is totally safe and appropriate.

--- Can someone confirm this statement? Please upvote, if so
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