added the grapheme_levenshtein polyfill (closes #555)

src/Intl/Grapheme/Grapheme.php

@@ -11,7 +11,12 @@
 
 namespace Symfony\Polyfill\Intl\Grapheme;
 
-\define('SYMFONY_GRAPHEME_CLUSTER_RX', ((float) \PCRE_VERSION < 10 ? (float) \PCRE_VERSION >= 8.32 : (float) \PCRE_VERSION >= 10.39) ? '\X' : Grapheme::GRAPHEME_CLUSTER_RX);
+\define('SYMFONY_GRAPHEME_CLUSTER_RX',
+    (false !== @preg_match('/\X/u', "a"))
+        ? '\X'
+        : Grapheme::GRAPHEME_CLUSTER_RX
+);
+
 
 /**
  * Partial intl implementation in pure PHP.
@@ -222,6 +227,82 @@ public static function grapheme_str_split($s, $len = 1)
 
         return $chunks;
     }
+        /**
+     * @param string $string1
+     * @param string $string2
+     * @param int    $insertion_cost
+     * @param int    $replacement_cost
+     * @param int    $deletion_cost
+     *
+     * @return int|false
+     *
+     * @see https://wiki.php.net/rfc/grapheme_levenshtein
+     */
+    public static function grapheme_levenshtein($string1, $string2, $insertion_cost = 1, $replacement_cost = 1, $deletion_cost = 1)
+    {
+        // Cast (PHP does this)
+        $string1 = (string) $string1;
+        $string2 = (string) $string2;
+        $insertion_cost = (int) $insertion_cost;
+        $replacement_cost = (int) $replacement_cost;
+        $deletion_cost = (int) $deletion_cost;
+
+        // Validate UTF-8 (RFC: return false if invalid)
+        if (1 !== preg_match('//u', $string1) || 1 !== preg_match('//u', $string2)) {
+            return false;
+        }
+
+        // Costs must be >= 0
+        if ($insertion_cost < 0 || $replacement_cost < 0 || $deletion_cost < 0) {
+            if (\PHP_VERSION_ID < 80000) {
+                return false;
+            }
+            throw new \ValueError('grapheme_levenshtein(): costs must be greater than or equal to 0');
+        }
+
+        // Grapheme cluster segmentation (same logic as grapheme_str_split)
+        preg_match_all('/(' . SYMFONY_GRAPHEME_CLUSTER_RX . ')/u', $string1, $m1);
+        preg_match_all('/(' . SYMFONY_GRAPHEME_CLUSTER_RX . ')/u', $string2, $m2);
+
+        $a = $m1[0] ?? [];
+        $b = $m2[0] ?? [];
+
+        $lenA = count($a);
+        $lenB = count($b);
+
+        // Edge cases
+        if (0 === $lenA) {
+            return $lenB * $insertion_cost;
+        }
+        if (0 === $lenB) {
+            return $lenA * $deletion_cost;
+        }
+
+        // Levenshtein DP matrix
+        $dp = array_fill(0, $lenA + 1, array_fill(0, $lenB + 1, 0));
+
+        for ($i = 1; $i <= $lenA; $i++) {
+            $dp[$i][0] = $dp[$i - 1][0] + $deletion_cost;
+        }
+        for ($j = 1; $j <= $lenB; $j++) {
+            $dp[0][$j] = $dp[0][$j - 1] + $insertion_cost;
+        }
+
+        for ($i = 1; $i <= $lenA; $i++) {
+            for ($j = 1; $j <= $lenB; $j++) {
+                $cost = ($a[$i - 1] === $b[$j - 1]) ? 0 : $replacement_cost;
+
+                $dp[$i][$j] = min(
+                    $dp[$i - 1][$j] + $deletion_cost,         // delete
+                    $dp[$i][$j - 1] + $insertion_cost,        // insert
+                    $dp[$i - 1][$j - 1] + $cost               // replace
+                );
+            }
+        }
+
+        return $dp[$lenA][$lenB];
+    }
+
 
     private static function grapheme_position($s, $needle, $offset, $mode)
     {

src/Intl/Grapheme/bootstrap.php

@@ -55,3 +55,11 @@ function grapheme_substr($string, $offset, $length = null) { return p\Grapheme::
 if (!function_exists('grapheme_str_split')) {
     function grapheme_str_split($string, $length = 1) { return p\Grapheme::grapheme_str_split($string, $length); }
 }
+
+if (!function_exists('grapheme_levenshtein')) {
+    function grapheme_levenshtein($string1, $string2, $insertion_cost = 1, $replacement_cost = 1, $deletion_cost = 1)
+    {
+        return Grapheme::grapheme_levenshtein($string1, $string2, $insertion_cost, $replacement_cost, $deletion_cost);
+    }
+}
+

src/Php85/bootstrap.php

@@ -10,6 +10,7 @@
  */
 
 use Symfony\Polyfill\Php85 as p;
+use Symfony\Polyfill\Intl\Grapheme\Grapheme;
 
 if (\PHP_VERSION_ID >= 80500) {
     return;
@@ -30,3 +31,10 @@ function array_first(array $array) { return p\Php85::array_first($array); }
 if (!function_exists('array_last')) {
     function array_last(array $array) { return p\Php85::array_last($array); }
 }
+
+if (\extension_loaded('intl') && !function_exists('grapheme_levenshtein')) {
+    function grapheme_levenshtein($string1, $string2, $insertion_cost = 1, $replacement_cost = 1, $deletion_cost = 1)
+    {
+        return Grapheme::grapheme_levenshtein($string1, $string2, $insertion_cost, $replacement_cost, $deletion_cost);
+    }
+}

tests/Intl/Grapheme/grapheme_levenshtein.phpt

@@ -0,0 +1,28 @@
+<?php
+
+use Symfony\Polyfill\Intl\Grapheme\Grapheme;
+
+return [
+    // Basic
+    [0, 'abc', 'abc'],
+    [1, 'abc', 'abd'],
+    [2, 'kitten', 'sitting'],
+
+    // Multibyte
+    [1, 'àbc', 'abc'],
+    [2, 'àbç', 'aBc'],
+
+    // Emoji
+    [0, '😊', '😊'],
+    [1, '😊', '😂'],
+    [1, "👨‍👩‍👧‍👦", "👨‍👩‍👦"],
+
+    // Empty
+    [0, '', ''],
+    [3, '', 'abc'],
+    [4, '', "👨‍👩‍👧‍👦"],
+
+    // Different lengths
+    [3, 'foo', 'foobar'],
+    [1, "🙂🙂", "🙂"],
+];