diff --git a/.changeset/starts-with-ends-with-operators.md b/.changeset/starts-with-ends-with-operators.md
new file mode 100644
index 0000000..29abf1d
--- /dev/null
+++ b/.changeset/starts-with-ends-with-operators.md
@@ -0,0 +1,7 @@
+---
+"posthog-php": minor
+---
+
+Support the `starts_with`, `not_starts_with`, `ends_with`, and `not_ends_with` property filter operators in feature flag local evaluation. Matching is case-insensitive and mirrors `icontains`. Previously, local evaluation treated these operators as unrecognized and silently evaluated their conditions to `false`; they now match correctly.
+
+Operators local evaluation doesn't recognize now throw `InconclusiveMatchException`, deferring the flag to the `/flags` endpoint instead of producing a silently wrong `false` — so operators the server adds in the future degrade gracefully.
diff --git a/lib/FeatureFlag.php b/lib/FeatureFlag.php
index b82a4fb..55f6e4c 100644
--- a/lib/FeatureFlag.php
+++ b/lib/FeatureFlag.php
@@ -57,6 +57,22 @@ public static function matchProperty($property, $propertyValues)
             return strpos(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value))) == false;
         }
 
+        if ($operator == "starts_with") {
+            return str_starts_with(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value)));
+        }
+
+        if ($operator == "not_starts_with") {
+            return !str_starts_with(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value)));
+        }
+
+        if ($operator == "ends_with") {
+            return str_ends_with(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value)));
+        }
+
+        if ($operator == "not_ends_with") {
+            return !str_ends_with(strtolower(FeatureFlag::valueToString($overrideValue)), strtolower(FeatureFlag::valueToString($value)));
+        }
+
         if (in_array($operator, ["regex", "not_regex"])) {
             $regexValue = FeatureFlag::prepareValueForRegex($value);
             if (FeatureFlag::isRegularExpression($regexValue)) {
@@ -157,7 +173,7 @@ public static function matchProperty($property, $propertyValues)
                 && FeatureFlag::compareSemverTuples($overrideTuple, $upper) < 0;
         }
 
-        return false;
+        throw new InconclusiveMatchException("Unknown operator: " . $operator);
     }
 
     /**
diff --git a/test/FeatureFlagLocalEvaluationTest.php b/test/FeatureFlagLocalEvaluationTest.php
index cb9cc89..ee7064b 100644
--- a/test/FeatureFlagLocalEvaluationTest.php
+++ b/test/FeatureFlagLocalEvaluationTest.php
@@ -333,6 +333,246 @@ public function testMatchPropertyContains(): void
         ]));
     }
 
+    public function testMatchPropertyStartsWith(): void
+    {
+        $prop = [
+            "key" => "key",
+            "value" => "Val",
+            "operator" => "starts_with"
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "value",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "VALUE",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "vaLue4",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "prevalue",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "Alakazam",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => 123,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => null,
+        ]));
+
+        $prop = [
+            "key" => "key",
+            "value" => 3,
+            "operator" => "starts_with"
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "3",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => 323,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => 123,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "val3",
+        ]));
+
+        $prop = [
+            "key" => "key",
+            "value" => "Val",
+            "operator" => "not_starts_with"
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "value",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "VALUE",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "prevalue",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "Alakazam",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => null,
+        ]));
+
+        // Case folding is ASCII-only, mirroring the flags service: non-ASCII
+        // characters do not match across case.
+        $prop = [
+            "key" => "key",
+            "value" => "ä",
+            "operator" => "starts_with"
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "ÄBC",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "äbc",
+        ]));
+    }
+
+    public function testMatchPropertyEndsWith(): void
+    {
+        $prop = [
+            "key" => "key",
+            "value" => "lUe",
+            "operator" => "ends_with"
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "value",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "VALUE",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "343tfvalue",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "value2",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "Alakazam",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => 123,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => null,
+        ]));
+
+        $prop = [
+            "key" => "key",
+            "value" => 3,
+            "operator" => "ends_with"
+        ];
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "3",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => 323,
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => 13,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => 321,
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "3val",
+        ]));
+
+        $prop = [
+            "key" => "key",
+            "value" => "lUe",
+            "operator" => "not_ends_with"
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "value",
+        ]));
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "VALUE",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "value2",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "Alakazam",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => null,
+        ]));
+
+        // Case folding is ASCII-only, mirroring the flags service: non-ASCII
+        // characters do not match across case.
+        $prop = [
+            "key" => "key",
+            "value" => "é",
+            "operator" => "ends_with"
+        ];
+
+        self::assertFalse(FeatureFlag::matchProperty($prop, [
+            "key" => "CAFÉ",
+        ]));
+
+        self::assertTrue(FeatureFlag::matchProperty($prop, [
+            "key" => "café",
+        ]));
+    }
+
+    public function testMatchPropertyUnknownOperatorIsInconclusive(): void
+    {
+        $prop = [
+            "key" => "key",
+            "value" => "value",
+            "operator" => "future_operator"
+        ];
+
+        $this->expectException(InconclusiveMatchException::class);
+        FeatureFlag::matchProperty($prop, [
+            "key" => "value",
+        ]);
+    }
+
+    public function testMatchPropertyStartsWithEndsWithMissingKeyIsInconclusive(): void
+    {
+        foreach (["starts_with", "not_starts_with", "ends_with", "not_ends_with"] as $operator) {
+            $prop = [
+                "key" => "key",
+                "value" => "Val",
+                "operator" => $operator
+            ];
+
+            try {
+                FeatureFlag::matchProperty($prop, [
+                    "key2" => "value",
+                ]);
+                self::fail("Expected InconclusiveMatchException for operator {$operator}");
+            } catch (InconclusiveMatchException $exception) {
+                self::assertInstanceOf(InconclusiveMatchException::class, $exception);
+            }
+        }
+    }
+
     public function testMatchPropertyRegex(): void
     {
         $prop = [