为什么会给出未定义的索引错误？

Question

if(isset($_POST['dino_c']) AND isset($_POST['dino_box']) AND isset($dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$_POST['dino_box']])){
if(....){
if(($pop>(0-1+$dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$_POST['dino_box']][4])) AND ($resource[0]>(0-1+$dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][5] -1)) AND ($resource[1]>(0-1+$dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][6] -1)) AND ($resource[2]>(0-1+$dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][7] -1))){
.
.
.
.
$pop = $pop - $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$_POST['dino_box']][4];
$pop_consum = $pop_consum + $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$_POST['dino_box']][4];
$resource[0] = 0 + $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][5];
$resource[1] = 0 + $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][6];
$resource[2] = 0 + $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][7];
$dino_add[$a_dino[$_POST['dino_c']][1]-1] = 0 + $dino_recruit[$a_dino[$_POST['dino_c']][1]][$a_dino[$_POST['dino_c']][3]][$a_dino[$_POST['dino_box']]][0];
.
.
.
.
}
}
}

这是我的代码，当我使用它时：

> undefined index:4 in .... ajax.php on line 672  => here line 3
> undefined index: in .... ajax.php on line 672  => here line 3
> undefined index:4 in .... ajax.php on line 672  => here line 3
> undefined index: in .... ajax.php on line 672  => here line 3
> undefined index:4 in .... ajax.php on line 672  => here line 3
> undefined index: in .... ajax.php on line 672  => here line 3
> undefined index:4 in .... ajax.php on line 679  => here line 10
> undefined index: in .... ajax.php on line 679  => here line 10
....
> undefined index:4 in .... ajax.php on line 682  => here line 13
> undefined index: in .... ajax.php on line 682  => here line 13

我使用isset()检查我的数据。如果都设置好了，为什么会产生错误？

在这段代码中，我们有两个$_POST，它们在第一行被检查，其他数据是数组，我检查了100次，我看不出哪里有错误。请参见第8行和第9行。它们没有错误。虽然它的结构与其他lines.Why相似？

Answer 1

当你使用isset($r['t']['b']['v']);时

它假定$r['t']['b']已经存在，并且只检查['v']。

如果这些['t']或['b']都不存在，PHP将发出警告，即使它在isset中也是如此。

所以要检查这样的多个dim数组实际上是：

if(isset($r['t'])&&isset($r['t']['b'])&&isset($r['t']['b']['v'])){...