diff --git a/tests/PHPStan/Analyser/nsrt/bug-4662.php b/tests/PHPStan/Analyser/nsrt/bug-4662.php
new file mode 100644
index 00000000000..071c3204e53
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-4662.php
@@ -0,0 +1,117 @@
+<?php
+
+namespace Bug4662;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+
+	/** @var \DateTimeImmutable|null */
+	private $programStartDate;
+
+	public function getProgramStartDate(): ?\DateTimeImmutable
+	{
+		return $this->programStartDate;
+	}
+
+}
+
+function testParenthesized(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// Correct: with parentheses, the assignment happens in the left side of &&
+	// and the narrowed variable is available in the right side
+	if ((null !== $programStartDate = $foo->getProgramStartDate()) && $now > $programStartDate) {
+		assertType('DateTimeImmutable', $programStartDate);
+	}
+}
+
+function testParenthesizedReversed(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// Correct: reversed comparison style
+	if (($programStartDate = $foo->getProgramStartDate()) !== null && $now > $programStartDate) {
+		assertType('DateTimeImmutable', $programStartDate);
+	}
+}
+
+function testWithLogicalAnd(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// 'and' has lower precedence than '=', so this parses as:
+	// (null !== ($programStartDate = $foo->getProgramStartDate())) and ($now > $programStartDate)
+	if (null !== $programStartDate = $foo->getProgramStartDate() and $now > $programStartDate) {
+		assertType('DateTimeImmutable', $programStartDate);
+	}
+}
+
+function testChained(Foo $foo): void
+{
+	// Multiple assignments chained with &&
+	if ((null !== $a = $foo->getProgramStartDate()) && (null !== $b = $foo->getProgramStartDate()) && $a > $b) {
+		assertType('DateTimeImmutable', $a);
+		assertType('DateTimeImmutable', $b);
+	}
+}
+
+function testFalseCheck(string $haystack, string $needle): void
+{
+	// false !== with assignment and &&
+	if ((false !== $pos = strpos($haystack, $needle)) && $pos > 5) {
+		assertType('int<6, max>', $pos);
+	}
+}
+
+function testWithOr(Foo $foo): void
+{
+	// Using || with === null (the inverse pattern)
+	if (($programStartDate = $foo->getProgramStartDate()) === null || $programStartDate->getTimestamp() < 0) {
+		assertType('DateTimeImmutable|null', $programStartDate);
+	} else {
+		assertType('DateTimeImmutable', $programStartDate);
+	}
+}
+
+function testLogicalOr(Foo $foo): void
+{
+	// 'or' has lower precedence than '='
+	if (null === $programStartDate = $foo->getProgramStartDate() or $programStartDate->getTimestamp() < 0) {
+		assertType('DateTimeImmutable|null', $programStartDate);
+	} else {
+		assertType('DateTimeImmutable', $programStartDate);
+	}
+}
+
+function testNested(Foo $foo): void
+{
+	// Assignment result used in chained &&
+	if ((null !== $a = $foo->getProgramStartDate()) && ($b = $a->format('Y-m-d')) !== '') {
+		assertType('DateTimeImmutable', $a);
+		assertType('non-falsy-string', $b);
+	}
+}
+
+function testAssignInWhile(Foo $foo): void
+{
+	// Assignment in while condition with &&
+	$i = 0;
+	while ((null !== $val = $foo->getProgramStartDate()) && $i < 10) {
+		assertType('DateTimeImmutable', $val);
+		$i++;
+	}
+}
+
+function testSimpleAssignInCondition(Foo $foo): void
+{
+	// Simple assignment in condition without &&
+	if (null !== $programStartDate = $foo->getProgramStartDate()) {
+		assertType('DateTimeImmutable', $programStartDate);
+	} else {
+		assertType('null', $programStartDate);
+	}
+	assertType('DateTimeImmutable|null', $programStartDate);
+}
diff --git a/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php b/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
index 67f77fa6bfe..63a6802713d 100644
--- a/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
+++ b/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
@@ -1626,4 +1626,18 @@ public function testBug6833(): void
 		]);
 	}
 
+	public function testBug4662(): void
+	{
+		$this->cliArgumentsVariablesRegistered = true;
+		$this->polluteScopeWithLoopInitialAssignments = false;
+		$this->checkMaybeUndefinedVariables = true;
+		$this->polluteScopeWithAlwaysIterableForeach = true;
+		$this->analyse([__DIR__ . '/data/bug-4662.php'], [
+			[
+				'Undefined variable: $programStartDate',
+				27,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Variables/data/bug-4662.php b/tests/PHPStan/Rules/Variables/data/bug-4662.php
new file mode 100644
index 00000000000..71385159cd6
--- /dev/null
+++ b/tests/PHPStan/Rules/Variables/data/bug-4662.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Bug4662Rule;
+
+class Foo
+{
+
+	/** @var \DateTimeImmutable|null */
+	private $programStartDate;
+
+	public function getProgramStartDate(): ?\DateTimeImmutable
+	{
+		return $this->programStartDate;
+	}
+
+}
+
+function testUnparenthesized(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// Without parentheses, && has higher precedence than =
+	// so this parses as: null !== ($programStartDate = (getProgramStartDate() && ($now > $programStartDate)))
+	// $programStartDate is used inside the BooleanAnd RHS before it's assigned
+	if (
+		null !== $programStartDate = $foo->getProgramStartDate()
+		&& $now > $programStartDate
+	) {
+		echo 'ok';
+	}
+}
+
+function testParenthesized(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// With parentheses, this works correctly - no undefined variable
+	if (
+		(null !== $programStartDate = $foo->getProgramStartDate())
+		&& $now > $programStartDate
+	) {
+		echo 'ok';
+	}
+}
+
+function testLogicalAnd(Foo $foo): void
+{
+	$now = new \DateTimeImmutable('now');
+
+	// 'and' has lower precedence than '=' so this works without extra parentheses
+	if (
+		null !== $programStartDate = $foo->getProgramStartDate()
+		and $now > $programStartDate
+	) {
+		echo 'ok';
+	}
+}