I18N: Add wp_search_term filter to allow per-term normalization

src/wp-includes/class-wp-query.php

@@ -1576,6 +1576,24 @@ protected function parse_search_terms( $terms ) {
 				continue;
 			}
 
+			/**
+			 * Filters a search term after it has passed the length and stopwords checks.
+			 *
+			 * Can be used to normalize or remove a term. Returning an empty string
+			 * will cause the term to be skipped. This is particularly useful for
+			 * languages such as Arabic that require stripping diacritics, Hamza
+			 * variants, or other decorative characters before meaningful comparison.
+			 *
+			 * @since 6.9.0
+			 *
+			 * @param string $term The search term.
+			 */
+			$term = apply_filters( 'wp_search_term', $term );
+
+			if ( ! $term ) {
+				continue;
+			}
+
 			$checked[] = $term;
 		}
 

tests/phpunit/tests/query/search.php

@@ -644,4 +644,35 @@ public function test_wp_query_removes_filter_wp_allow_query_attachment_by_filena
 	public function filter_posts_search( $sql ) {
 		return $sql . ' /* posts_search */';
 	}
+
+	/**
+	 * @ticket 25585
+	 */
+	public function test_wp_search_term_filter_empty_string_removes_term() {
+		$callback = static function ( $term ) {
+			return 'foo' === $term ? '' : $term;
+		};
+
+		add_filter( 'wp_search_term', $callback );
+		$query = new WP_Query( array( 's' => 'foo bar' ) );
+		remove_filter( 'wp_search_term', $callback );
+
+		$this->assertSame( array( 'bar' ), $query->get( 'search_terms' ) );
+	}
+
+	/**
+	 * @ticket 25585
+	 */
+	public function test_wp_search_term_filter_normalizes_arabic_characters() {
+		$callback = static function ( $term ) {
+			$term = str_replace( array( 'أ', 'إ', 'آ' ), 'ا', $term );
+			return str_replace( array( 'َ', 'ً', 'ُ', 'ٌ', 'ِ', 'ٍ', 'ْ', 'ّ' ), '', $term );
+		};
+
+		add_filter( 'wp_search_term', $callback );
+		$query = new WP_Query( array( 's' => 'أَنْتَ بَيْت' ) );
+		remove_filter( 'wp_search_term', $callback );
+
+		$this->assertSame( array( 'انت', 'بيت' ), $query->get( 'search_terms' ) );
+	}
 }