列表空间 - 错误

Question

当我编译此代码第 36 行的符号时，我得到一个奇怪的符号：

我不知道你按了什么才能得到那个可以写代码的漂亮框。请不要给我差评。编辑帖子。我尝试用 4 个空格插入代码，但似乎不起作用。抱歉给您带来不便。

\documentclass{article}
   \usepackage{listings,xcolor}
   \definecolor{dkgreen}{rgb}{0,.6,0}
   \definecolor{dkblue}{rgb}{0,0,.6}
   \definecolor{dkyellow}{cmyk}{0,0,.8,.3}

   \lstset{
     language        = php,
     basicstyle      = \small\ttfamily,
     keywordstyle    = \color{dkblue},
     stringstyle     = \color{red},
     identifierstyle = \color{dkgreen},
     commentstyle    = \color{gray},
     emph            =[1]{php},
     emphstyle       =[1]\color{black},
     emph            =[2]{if,and,or,else},
     emphstyle       =[2]\color{dkyellow}}

   \begin{document}
   \begin{lstlisting}
   <?php

   $username = $_POST["username"];
   $password = $_POST["password"];

   $pass = md5($passwort);

   // another comment
   if($username=="User" and
   $pass=="123456")
       {
       echo "Welcome";
       }
    else
       {
       echo "Try again.";
       }
    ?>
    \end{lstlisting}
    \end{document}

Answer 1

字符串中出现了空格。要消除空格，请使用选项中的showstringspaces=false(initially )。true

\documentclass{article}
   \usepackage{listings,xcolor}
   \definecolor{dkgreen}{rgb}{0,.6,0}
   \definecolor{dkblue}{rgb}{0,0,.6}
   \definecolor{dkyellow}{cmyk}{0,0,.8,.3}

   \lstset{
     language        = php,
     basicstyle      = \small\ttfamily,
     keywordstyle    = \color{dkblue},
     stringstyle     = \color{red},
     identifierstyle = \color{dkgreen},
     commentstyle    = \color{gray},
     emph            =[1]{php},
     emphstyle       =[1]\color{black},
     emph            =[2]{if,and,or,else},
     showstringspaces=false,                   %% <--- here
     emphstyle       =[2]\color{dkyellow}}

   \begin{document}
   \begin{lstlisting}
   <?php

   $username = $_POST["username"];
   $password = $_POST["password"];

   $pass = md5($passwort);

   // another comment
   if($username=="User" and
   $pass=="123456")
       {
       echo "Welcome";
       }
    else
       {
       echo "Try again.";
       }
    ?>
    \end{lstlisting}
    \end{document}