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fix: don't sort condition sets with variant overrides to the top #85

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Merged
andyzzhao merged 1 commit into from
Sep 26, 2025
Merged

fix: don't sort condition sets with variant overrides to the top #85

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47 changes: 1 addition & 46 deletions lib/FeatureFlag.php
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Original file line number Diff line number Diff line change
Expand Up @@ -337,57 +337,12 @@ private static function variantLookupTable($featureFlag)
return $lookupTable;
}

private static function compareFlagConditions($conditionA, $conditionB)
{
$AhasVariantOverride = isset($conditionA["variant"]);
$BhasVariantOverride = isset($conditionB["variant"]);

if ($AhasVariantOverride && $BhasVariantOverride) {
return 0;
} elseif ($AhasVariantOverride) {
return -1;
} elseif ($BhasVariantOverride) {
return 1;
} else {
return 0;
}
}

public static function matchFeatureFlagProperties($flag, $distinctId, $properties, $cohorts = [], $flagsByKey = null, $evaluationCache = null)
{
$flagConditions = ($flag["filters"] ?? [])["groups"] ?? [];
$isInconclusive = false;

// Add index to each condition to make stable sort possible
$flagConditionsWithIndexes = array();
$i = 0;
foreach ($flagConditions as $key => $value) {
$flagConditionsWithIndexes[] = array($value, $i);
$i++;
}
// # Stable sort conditions with variant overrides to the top.
// # This ensures that if overrides are present, they are
// # evaluated first, and the variant override is applied to the first matching condition.
usort(
$flagConditionsWithIndexes,
function ($conditionA, $conditionB) {
$AhasVariantOverride = isset($conditionA[0]["variant"]);
$BhasVariantOverride = isset($conditionB[0]["variant"]);

if ($AhasVariantOverride && $BhasVariantOverride) {
return $conditionA[1] - $conditionB[1];
} elseif ($AhasVariantOverride) {
return -1;
} elseif ($BhasVariantOverride) {
return 1;
} else {
return $conditionA[1] - $conditionB[1];
}
}
);

foreach ($flagConditionsWithIndexes as $conditionWithIndex) {
$condition = $conditionWithIndex[0];
foreach ($flagConditions as $condition) {
try {
if (FeatureFlag::isConditionMatch($flag, $distinctId, $condition, $properties, $cohorts, $flagsByKey, $evaluationCache)) {
$variantOverride = $condition["variant"] ?? null;
Expand Down
11 changes: 6 additions & 5 deletions test/FeatureFlagLocalEvaluationTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1706,9 +1706,9 @@ public function testFlagWithInvalidVariantOverrides()
$this->assertEquals(PostHog::getFeatureFlag('beta-feature', 'example_id'), "second-variant");
}

public function testFlagWithMultipleVariantOverrides()
public function testConditionsEvaluatedInOrder()
{
$this->http_client = new MockedHttpClient(host: "app.posthog.com", flagEndpointResponse: MockedResponses::LOCAL_EVALUATION_MULTIPLE_VARIANT_OVERRIDES_REQUEST);
$this->http_client = new MockedHttpClient(host: "app.posthog.com", flagEndpointResponse: MockedResponses::LOCAL_EVALUATION_CONDITIONS_ORDER_REQUEST);
$this->client = new Client(
self::FAKE_API_KEY,
[
Expand All @@ -1719,9 +1719,10 @@ public function testFlagWithMultipleVariantOverrides()
);
PostHog::init(null, null, $this->client);

$this->assertEquals(PostHog::getFeatureFlag('beta-feature', 'test_id', [], ["email" => "test@posthog.com"]), "second-variant");
$this->assertEquals(PostHog::getFeatureFlag('beta-feature', 'example_id'), "third-variant");
$this->assertEquals(PostHog::getFeatureFlag('beta-feature', 'another_id'), "second-variant");
// VIP users now match the first condition (100% rollout) instead of their specific variant override
// because conditions are evaluated in order
$result = PostHog::getFeatureFlag('test-flag', 'vip_user', [], ["email" => "user@vip.com"]);
$this->assertTrue(in_array($result, ['control', 'test'])); // Should get one of the regular variants, not vip-variant
}

public function testEventCalled()
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56 changes: 56 additions & 0 deletions test/assests/MockedResponses.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1050,6 +1050,62 @@ class MockedResponses
],
];

public const LOCAL_EVALUATION_CONDITIONS_ORDER_REQUEST = [
'count' => 1,
'next' => null,
'previous' => null,
'flags' => [
[
"id" => 1,
"name" => "Test Flag",
"key" => "test-flag",
"active" => true,
"deleted" => false,
"filters" => [
"groups" => [
// First condition: 100% rollout for everyone
[
"rollout_percentage" => 100,
],
// Second condition: VIP users get a specific variant
// This used to be evaluated first due to sorting, but now it's evaluated second
[
"properties" => [
[
"key" => "email",
"value" => "@vip.com",
"operator" => "icontains",
"type" => "person"
]
],
"rollout_percentage" => 100,
"variant" => "vip-variant"
],
],
"multivariate" => [
"variants" => [
[
"key" => "control",
"name" => "Control",
"rollout_percentage" => 50
],
[
"key" => "test",
"name" => "Test",
"rollout_percentage" => 50
],
[
"key" => "vip-variant",
"name" => "VIP Variant",
"rollout_percentage" => 0
]
]
]
],
]
],
];


public const EXPERIENCE_CONITNUITY_REQUEST = [
'count' => 1,
Expand Down