fix(flags): align local string matching with the flags service

.changeset/local-flag-case-folding.md

@@ -0,0 +1,5 @@
+---
+"posthog-php": patch
+---
+
+Match local feature flag ASCII and Unicode case handling and numeric stringification with the flags service.

composer.json

@@ -16,7 +16,9 @@
 	"require": {
 		"ext-json": "*",
 		"php": ">=8.2",
-		"symfony/clock": "^6.2|^7.0|^8.0"
+		"symfony/clock": "^6.2|^7.0|^8.0",
+		"symfony/polyfill-mbstring": "^1.31",
+		"symfony/polyfill-iconv": "^1.31"
 	},
 	"require-dev": {
 		"phpunit/phpunit": "^11.0",

lib/FeatureFlag.php

@@ -54,7 +54,7 @@ public static function matchProperty($property, $propertyValues)
         }
 
         if ($operator == "not_icontains") {
-            return strpos(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value))) == false;
+            return strpos(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value))) === false;
         }
 
         if ($operator == "starts_with") {
@@ -557,19 +557,43 @@ private static function convertToDateTime($value)
 
     private static function computeExactMatch($value, $overrideValue)
     {
+        $overrideString = FeatureFlag::unicodeLowercase(FeatureFlag::valueToString($overrideValue));
         if (is_array($value)) {
-            return in_array(strtolower(FeatureFlag::valueToString($overrideValue)), array_map('strtolower', array_map(fn($val) => FeatureFlag::valueToString($val), $value)));
+            foreach ($value as $candidate) {
+                if (FeatureFlag::unicodeLowercase(FeatureFlag::valueToString($candidate)) === $overrideString) {
+                    return true;
+                }
+            }
+            return false;
         }
-        return strtolower(FeatureFlag::valueToString($value)) == strtolower(FeatureFlag::valueToString($overrideValue));
+        return FeatureFlag::unicodeLowercase(FeatureFlag::valueToString($value)) === $overrideString;
+    }
+
+    private static function unicodeLowercase($value)
+    {
+        // Rust's full, context-independent lowercase expands U+0130, while PHP's
+        // simple mode does not. Expand it before applying simple lowercase.
+        $value = str_replace("\u{0130}", "i\u{0307}", $value);
+
+        // The polyfill does not define MB_CASE_LOWER_SIMPLE, but its regular
+        // lowercase mapping is context-independent and therefore equivalent here.
+        $mode = defined('MB_CASE_LOWER_SIMPLE') ? MB_CASE_LOWER_SIMPLE : MB_CASE_LOWER;
+        return mb_convert_case($value, $mode, "UTF-8");
     }
 
     private static function valueToString($value)
     {
         if (is_bool($value)) {
             return $value ? "true" : "false";
-        } else {
-            return strval($value);
         }
+        if (is_float($value)) {
+            if (!is_finite($value)) {
+                return strval($value);
+            }
+            $encoded = json_encode($value, JSON_PRESERVE_ZERO_FRACTION | JSON_THROW_ON_ERROR);
+            return preg_replace('/\.0(e[+-]?\d+)$/', '$1', $encoded);
+        }
+        return strval($value);
     }
 
     private static function compare($lhs, $rhs, $operator, $type = "string")

test/FeatureFlagLocalEvaluationTest.php

@@ -248,6 +248,65 @@ public function testMatchPropertyNotIn(): void
         ]);
     }
 
+    public function testMatchPropertyExactUsesUnicodeLowercase(): void
+    {
+        $exact = [
+            "key" => "key",
+            "value" => "Ä",
+            "operator" => "exact",
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => "ä"]));
+
+        $exact["value"] = "İ";
+        self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => "i\u{0307}"]));
+        self::assertFalse(FeatureFlag::matchProperty($exact, ["key" => "i"]));
+
+        $exact["value"] = ["FREE", "Ä"];
+        self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => "ä"]));
+
+        $isNot = $exact;
+        $isNot["operator"] = "is_not";
+        self::assertFalse(FeatureFlag::matchProperty($isNot, ["key" => "ä"]));
+
+        foreach ([["ß", "ss"], ["Σ", "ς"], ["ΟΣ", "ος"]] as [$filter, $property]) {
+            $exact["value"] = $filter;
+            self::assertFalse(FeatureFlag::matchProperty($exact, ["key" => $property]));
+
+            $isNot["value"] = $filter;
+            self::assertTrue(FeatureFlag::matchProperty($isNot, ["key" => $property]));
+        }
+
+        $exact["value"] = "ΟΣ";
+        self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => "οσ"]));
+    }
+
+    public function testMatchPropertyStringificationPreservesIntegralFloats(): void
+    {
+        $exact = [
+            "key" => "key",
+            "value" => "323.0",
+            "operator" => "exact",
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => 323.0]));
+        self::assertFalse(FeatureFlag::matchProperty($exact, ["key" => 323]));
+
+        $endsWith = [
+            "key" => "key",
+            "value" => "3",
+            "operator" => "ends_with",
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($endsWith, ["key" => 323.0]));
+        self::assertTrue(FeatureFlag::matchProperty($endsWith, ["key" => 323]));
+
+        foreach ([["1e+20", 1.0e20], ["-1e-7", -1.0e-7], ["INF", INF], ["NAN", NAN]] as [$filter, $property]) {
+            $exact["value"] = $filter;
+            self::assertTrue(FeatureFlag::matchProperty($exact, ["key" => $property]));
+        }
+    }
+
     /**
      * @dataProvider presentPresenceOperatorValuesProvider
      */
@@ -352,6 +411,24 @@ public function testMatchPropertyContains(): void
         self::assertFalse(FeatureFlag::matchProperty($prop, [
             "key" => "three",
         ]));
+
+        // Case folding is ASCII-only, mirroring the flags service.
+        $prop["value"] = "ä";
+        self::assertFalse(FeatureFlag::matchProperty($prop, ["key" => "ÄBC"]));
+        self::assertTrue(FeatureFlag::matchProperty($prop, ["key" => "äbc"]));
+    }
+
+    public function testMatchPropertyNotContainsNegatesMatchAtOffsetZero(): void
+    {
+        $prop = [
+            "key" => "key",
+            "value" => "VALUE",
+            "operator" => "not_icontains",
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, ["key" => "value suffix"]));
+        self::assertFalse(FeatureFlag::matchProperty($prop, ["key" => "prefix value suffix"]));
+        self::assertTrue(FeatureFlag::matchProperty($prop, ["key" => "different"]));
     }
 
     public function testMatchPropertyStartsWith(): void