// Before
$position = strrpos($subject, (string) $search);
return substr($subject, $position + strlen($search));

// After
$position = mb_strrpos($subject, $search);
return static::substr($subject, $position + static::length($search));

$this->assertSame('', Str::afterLast('café au café', 'café'));
$this->assertSame('', Str::afterLast('こんにちは世界こんにちは', 'こんにちは'));