Post: Ensure get_post_custom_values() non-array returns grace fully.

src/wp-includes/post.php

@@ -2889,6 +2889,10 @@ function get_post_custom_values( $key = '', $post_id = 0 ) {
 
 	$custom = get_post_custom( $post_id );
 
+	if ( ! is_array( $custom ) ) {
+		return null;
+	}
+
 	return $custom[ $key ] ?? null;
 }
 

tests/phpunit/tests/post/getPostCustom.php

@@ -0,0 +1,99 @@
+<?php
+
+/**
+ * @group post
+ *
+ * @covers ::get_post_custom
+ */
+class Tests_Post_GetPostCustom extends WP_UnitTestCase {
+
+	protected static int $post_id;
+
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ): void {
+		self::$post_id = $factory->post->create();
+		add_post_meta( self::$post_id, 'test_key_1', 'value_a' );
+		add_post_meta( self::$post_id, 'test_key_1', 'value_b' );
+		add_post_meta( self::$post_id, 'test_key_2', 'value_c' );
+	}
+
+	/**
+	 * Test get_post_custom() happy path.
+	 */
+	public function test_get_post_custom_happy_path() {
+		$custom = get_post_custom( self::$post_id );
+
+		$this->assertIsArray( $custom );
+		$this->assertArrayHasKey( 'test_key_1', $custom );
+		$this->assertCount( 2, $custom['test_key_1'] );
+		$this->assertSame( array( 'value_a', 'value_b' ), $custom['test_key_1'] );
+	}
+
+	/**
+	 * Test get_post_custom_keys() happy path.
+	 */
+	public function test_get_post_custom_keys_happy_path() {
+		$keys = get_post_custom_keys( self::$post_id );
+
+		$this->assertIsArray( $keys );
+		$this->assertContains( 'test_key_1', $keys );
+		$this->assertContains( 'test_key_2', $keys );
+	}
+
+	/**
+	 * Test get_post_custom_values() happy path.
+	 */
+	public function test_get_post_custom_values_happy_path() {
+		$values = get_post_custom_values( 'test_key_1', self::$post_id );
+
+		$this->assertIsArray( $values );
+		$this->assertSame( array( 'value_a', 'value_b' ), $values );
+	}
+
+	/**
+	 * Test functions with non-existent post ID (The core of ticket #65044).
+	 *
+	 * @ticket 65044
+	 */
+	public function test_custom_functions_with_invalid_post_id() {
+		$invalid_id = 99999;
+
+		// get_post_custom returns empty array for non-existent post in current WP
+		$this->assertSame( array(), get_post_custom( $invalid_id ) );
+
+		// get_post_custom_keys returns null/void if array is empty/invalid
+		$this->assertNull( get_post_custom_keys( $invalid_id ) );
+
+		// get_post_custom_values should return null (Fix for #65044)
+		$this->assertNull( get_post_custom_values( 'test_key_1', $invalid_id ) );
+	}
+
+	/**
+	 * Test get_post_custom_values() with empty key.
+	 *
+	 * @ticket 65044
+	 */
+	public function test_get_post_custom_values_empty_key() {
+		$this->assertNull( get_post_custom_values( '', self::$post_id ) );
+		$this->assertNull( get_post_custom_values( null, self::$post_id ) );
+	}
+
+	/**
+	 * Test behavior when post_id is 0 and no global post is set.
+	 */
+	public function test_custom_functions_with_zero_id_no_global_post() {
+		// Ensure global post is null
+		$GLOBALS['post'] = null;
+
+		$custom = get_post_custom( 0 );
+		$this->assertEmpty( $custom, 'get_post_custom(0) should return an empty value (false or empty array).' );
+		$this->assertNull( get_post_custom_keys( 0 ) );
+		$this->assertNull( get_post_custom_values( 'test_key_1', 0 ) );
+	}
+
+	/**
+	 * Test get_post_custom_values() when key does not exist.
+	 */
+	public function test_get_post_custom_values_non_existent_key() {
+		$this->assertNull( get_post_custom_values( 'non_existent_key', self::$post_id ) );
+	}
+}