PHP Intl Extension — Unicode

Also Known As

TL;DR

Explanation

Intl extension (wrapping ICU): grapheme_strlen/grapheme_substr (correct for emoji and combining characters — 👨‍👩‍👧‍👦 = 1 grapheme, 7 code points), Normalizer (NFC/NFD Unicode normalisation — required before comparing or storing user text), Transliterator (convert between scripts — Cyrillic to Latin), IntlBreakIterator (word/sentence/character boundaries), IntlChar (Unicode character properties). The family emoji 👨‍👩‍👧‍👦 has 7 Unicode code points — mb_strlen returns 7, grapheme_strlen returns 1.

Common Misconception

Why It Matters

Common Mistakes

• strlen() for character limits on user input — counts bytes not characters
• mb_strlen() for grapheme-aware limits — counts code points not visible grapheme clusters
• Not normalising Unicode before storing — same visual character can have multiple representations causing duplicate key errors
• strtolower() for multilingual case conversion — use IntlChar or Transliterator

Code Examples

// Wrong character counting:
$input = 'Hello 👨‍👩‍👧‍👦'; // 1 visible emoji
$limit = 100;
if (mb_strlen($input) > $limit) { /* trim */ }
// mb_strlen: 'Hello ' = 6, family emoji = 7 code points = 13 total
// User sees 7 visible characters, system counts 13

// Grapheme-correct character counting:
$input = 'Hello 👨‍👩‍👧‍👦';
$limit = 100;
if (grapheme_strlen($input) > $limit) {
    $input = grapheme_substr($input, 0, $limit);
}
// grapheme_strlen: 'Hello ' = 6, family emoji = 1 = 7 total — correct!

// Normalise Unicode before storing to prevent duplicate keys:
$normalised = Normalizer::normalize($userInput, Normalizer::FORM_C);
$pdo->prepare('INSERT INTO users (name) VALUES (?)')->execute([$normalised]);

References

• ↗ https://www.php.net/manual/en/book.intl.php

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