求高手帮忙理解一段代码

Question

这个是discuz的安装程序的一段代码，有一点没弄明白，$ks[$level] = $ks[$level - 1]."['$key']";这里的$level - 1应该是-1啊，为什么断点输出的时候是0；求解释function buildarray($array, $level = 0, $pre = '$_config') {
static $ks;
if($level == 0) {
$ks = array();
$return = '';
} foreach ($array as $key => $val) {
if($level == 0) {
$newline = str_pad('  CONFIG '.strtoupper($key).'  ', 70, '-', STR_PAD_BOTH);
$return .= "\r\n// $newline //\r\n";
if($key == 'admincp') {
$newline = str_pad(' Founders: $_config[\'admincp\'][\'founder\'] = \'1,2,3\'; ', 70, '-', STR_PAD_BOTH);
$return .= "// $newline //\r\n";
}
}

$ks[$level] = $ks[$level - 1]."['$key']";

if(is_array($val)) {
$ks[$level] = $ks[$level - 1]."['$key']";
$return .= buildarray($val, $level + 1, $pre);
} else {
$val =  is_string($val) || strlen($val) > 12 || !preg_match("/^\-?[1-9]\d*$/", $val) ? '\''.addcslashes($val, '\'\\').'\'' : $val;
$return .= $pre.$ks[$level - 1]."['$key']"." = $val;\r\n";
}
}
print_r($ks);
return $return;
}

Answer 1

就是第一层，刚进来的时候，buildarray($array, $level = 0, $pre = '$_config') 最开始进来的时候$level就是0，那$level-1不就是-1吗，为什么输出的时候是$ks的索引是0而不是-1？

Answer 2

我把这个方法提出来后，发现$ks[$level - 1]的索引是-1,  discuz里面只有在这个方法里面声明了$ks，为什么他处理出来的结果就没有-1，怎么也搞不懂

Answer 3

你把 $array 打印出来看看

Answer 4

Array
(
    [db] => Array
        (
            [1] => Array
                (
                    [dbhost] => 127.0.0.1
                    [dbuser] => root
                    [dbpw] => 123
                    [dbcharset] => utf8
                    [pconnect] => 0
                    [dbname] => ultrax_7XhbMs
                    [tablepre] => pre_
                )            [common] => Array
                (
                    [slave_except_table] => 
                )            [slave] => Array
                (
                )            [map] => Array
                (
                )        )    [memory] => Array
        (
            [prefix] => vQbPi0_
            [eaccelerator] => 1
            [apc] => 1
            [xcache] => 1
            [memcache] => Array
                (
                    [server] => 
                    [port] => 11211
                    [pconnect] => 1
                    [timeout] => 1
                )        )    [server] => Array
        (
            [id] => 1
        )    [download] => Array
        (
            [readmod] => 2
            [xsendfile] => Array
                (
                    [type] => 0
                    [dir] => /down/
                )        )    [cache] => Array
        (
            [type] => sql
        )    [output] => Array
        (
            [charset] => utf-8
            [forceheader] => 1
            [gzip] => 0
            [tplrefresh] => 1
            [language] => zh_cn
            [staticurl] => static/
            [ajaxvalidate] => 0
            [iecompatible] => 0
        )    [cookie] => Array
        (
            [cookiepre] => AAvI_
            [cookiedomain] => 
            [cookiepath] => /
        )    [security] => Array
        (
            [authkey] => e926f18LJRxCMdzp
            [urlxssdefend] => 1
            [attackevasive] => 0
            [querysafe] => Array
                (
                    [status] => 1
                    [dfunction] => Array
                        (
                            [0] => load_file
                            [1] => hex
                            [2] => substring
                            [3] => if
                            [4] => ord
                            [5] => char
                        )                    [daction] => Array
                        (
                            [0] => intooutfile
                            [1] => intodumpfile
                            [2] => unionselect
                            [3] => (select
                            [4] => unionall
                            [5] => uniondistinct
                        )                    [dnote] => Array
                        (
                            [0] => /*
                            [1] => */
                            [2] => #
                            [3] => --
                            [4] => "
                        )                    [dlikehex] => 1
                    [afullnote] => 0
                )        )    [admincp] => Array
        (
            [founder] => 1
            [forcesecques] => 0
            [checkip] => 1
            [runquery] => 1
            [dbimport] => 1
        )    [remote] => Array
        (
            [on] => 0
            [dir] => remote
            [appkey] => 62cf0b3c3e6a4c9468e7216839721d8e
            [cron] => 0
        ))

Answer 5

    if($level == 0) {
        $ks = array();
        $return = '';
    }如果参数是默认值0，直接返回空字符串了，要执行下面的代码流程，，level参数必然是个非0值

Answer 6

但是$ks[$level-1]应该是$ks[-1]，我提出来后，就会报错，但是他为什么不报错，难道屏蔽了错误？

Answer 7

你没看到是
$ks[$level] = $ks[$level - 1]."['$key']";
吗？另有
    if($level == 0) {
        $ks = array();
递归时
buildarray($val, $level + 1, $pre);所以 $level 不可能小于 0
$ks[$level - 1] 也就不可能存在，$ks[$level - 1]只能是空