code: def t_quotedvar_DOLLAR_OPEN_CURLY_BRACES(t):
      r'\$\{'
      if re.match(r'[A-Za-z_]', peek(t.lexer)):
          t.lexer.begin('varname')
      else:
          t.lexer.begin('php')
      return f t_quotedvar_DOLLAR_OPEN_CURLY_BRACES(t):
      r'\$\{'
      if re.match(r'[A-Za-z_]', peek(t.lexer)):
          t.lexer.begin('varname')
      else:
          t.lexer.begin('php')
      return t
docs: r'\$\{