added mb_ pollyfils and added a test suite to ensure it still works

.github/workflows/unit-tests.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         operating-system: [ubuntu-latest]
-        php-versions: [ '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
+        php: [ '8.1', '8.2', '8.3', '8.4']
     runs-on: ${{ matrix.operating-system }}
     services:
       # Setup MYSQL
@@ -34,8 +34,12 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
+          extensions: ${{ matrix.php != '8.1' && 'mbstring' || '' }}
           tools: composer
 
+      - name: Show PHP version
+        run: php -v
+
       - name: Validate composer.json and composer.lock
         run: composer validate --strict
 

functions.php

@@ -21,6 +21,63 @@
 
 // region
 
+/**
+ * Polyfill for mb_strimwidth.
+ */
+if ( ! function_exists( 'mb_strimwidth' ) ) {
+	/**
+	 * Polyfill for mb_strimwidth.
+	 *
+	 * @param string  $source      The string to trim.
+	 * @param integer $start       The starting position.
+	 * @param integer $width       The width to trim to.
+	 * @param string  $trim_marker The marker to append if the string is trimmed.
+	 * @param string  $encoding    The character encoding.
+	 *
+	 * @return string
+	 */
+	function mb_strimwidth( $source, $start, $width, $trim_marker = '', $encoding = 'UTF-8' ) {
+		// Fallback using mb_substr if available
+		if ( function_exists( 'mb_substr' ) ) {
+			$substr = mb_substr( $source, $start, $width, $encoding );
+			if ( mb_strlen( $source, $encoding ) > $width ) {
+				return $substr . $trim_marker;
+			}
+			return $substr;
+		} else {
+			// Rough fallback using substr (not multibyte-safe!)
+			$substr = substr( $source, $start, $width );
+			if ( strlen( $source ) > $width ) {
+				return $substr . $trim_marker;
+			}
+			return $substr;
+		}
+	}
+}
+
+/**
+ * Polyfill for mb_strlen.
+ */
+if ( ! function_exists( 'mb_strlen' ) ) {
+	/**
+	 * Polyfill for mb_strlen.
+	 *
+	 * @param string $source   The string to measure.
+	 * @param string $encoding The character encoding.
+	 *
+	 * @return integer
+	 */
+	function mb_strlen( $source, $encoding = 'UTF-8' ) {
+		// Use preg_match_all to count UTF-8 characters
+		if ( 'UTF-8' === $encoding ) {
+			return preg_match_all( '/./u', $source, $matches );
+		}
+
+		// Fallback: use strlen (not multibyte-safe!)
+		return strlen( $source );
+	}
+}
+
 /**
  * Returns the plugin's main class instance.
  *

tests/Settings/Test_Settings.php

@@ -80,7 +80,7 @@ public function test_can_set_drop_tables_on_uninstall(): void {
 	public function test_can_set_and_get_migrations(): void {
 		$migration_1 = $this->createMock( Abstract_Migration::class );
 		$migration_2 = $this->createMock( Abstract_Migration::class );
-		$migrations  = array( $migration_1::class, $migration_2::class );
+		$migrations = [get_class($migration_1), get_class($migration_2)];
 		Settings::update_migrations( $migrations );
 		$this->assertEquals( $migrations, Settings::migrations() );
 	}

tests/Test_Functions.php

@@ -53,4 +53,5 @@ public static function normalize_url_provider(): array {
 	public function test_can_normalize_url( string $url, string $expected ): void {
 		$this->assertSame( $expected, \wpcomsp_wayback_link_fixer_normalize_url( $url ) );
 	}
+
 }