PHP syntax highlighting in lateX

%%%%%%%%%% basic settings %%%%%%%%%%%%

\documentclass[a4paper,12,oneside,openright] {scrreprt}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage[pdftex]{graphicx,color}
\usepackage{graphicx}
\usepackage{epsfig}         % pix
\usepackage{fancyhdr}
\usepackage{times}
\usepackage{url}
\usepackage{amsmath}
\usepackage{amsfonts}

\parindent=0cm
\parskip=1mm

%%%%%% syntax highlighting settings %%%%%%%%%%

\usepackage{listings,color}
\usepackage{textcomp}

\definecolor{lightgray}{gray}{0.95}
\definecolor{gray}{gray}{0.5}
\definecolor{green}{rgb}{0,0.5,0}
\definecolor{darkblue}{rgb}{0,0,0.5}
\definecolor{darkgreen}{rgb}{0,0.5,0}
\definecolor{orange}{rgb}{1,0.5,0}

\lstset{
backgroundcolor=\color{lightgray},
%numbers=left,
%numberstyle=\tiny,
%numbersep=5pt,
showstringspaces=false,
extendedchars=true,
tabsize=4,
sensitive=false,
%frame=leftline,
mathescape=false,
upquote=true
}

\lstset{
language=PHP,
keywordstyle=\color{blue}\bfseries,
otherkeywords={session_regenerate_id,fwrite,mysql_fetch_array,news_displayNews,myexec},
commentstyle=\color{orange}\ttfamily,
stringstyle=\color{red}\ttfamily,
identifierstyle=\color{darkblue},
emph={[6]if,while,switch,isset,empty,else,function},
emphstyle=[6]\color{darkgreen},
emph={[12]\ , \}, \{, [, ], =, +, -, <, >, ?, !},
emphstyle=[12]\color{darkgreen}\bfseries,
emph={[5]SELECT,INSERT,UNION,FROM,WHERE},
emphstyle=[5]\color{red}
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{lstlisting}[numbers=left,firstnumber=1,numbersep=-8pt,caption=Example 1]{PHP}
    <?php
        $a = $_GET['a'];
        $b = $a;
        system($b, $ret);
    ?>
\end{lstlisting}