动态网页技术PHP程序字符串处理函数

动态网页技术PHP程序字符串处理函数(3)         return $rev_str;
}

//字符串比较
function strcmp($s1,  $s2)
{
        if (strlen($s1) <  strlen($s2)) return -1 ;
        if (strlen($s1) > strlen( $s2)) return 1;
        for ($i =0; $i<strlen($s1 ); $i++){
                if ($s1[ $i] == $s2[$i]){
                        continue;
                }else{
                        return false;
                }
        }
        return  0;
}

//查找字符串
function  strstr($str, $substr)
{
         $m = strlen($str);
        $n = strlen($substr );
        if ($m < $n) return false ;
        for ($i=0; $i <=($m-$n+1); $i ++){
                $sub = substr( $str, $i, $n);
                if ( strcmp($sub, $substr) ==  0)  return $i;
        }
        return false ;
}

//字符串替换
function str_replace($substr , $newsubstr, $str)
{
         $m = strlen($str);