访问3D数组

Question

my understanding of php and how to use multi-dimensional arrays is limited so i am struggling to understand how to access name="value".

<input name='questions[]' type='text' value='question 1' /><br/>
  <input name='choice[1-1][]' type='text' value='option 1' />   
    <input name='value[1-1][1][]' type='text' value='value' /><br/>
  <input name='choice[1-1][]' type='text' value='option 2' />   
    <input name='value[1-1][2][]' type='text' value='value' /><br/>
  <input name='choice[1-1][]' type='text' value='option 3' />   
    <input name='value[1-1][3][]' type='text' value='value' /><br/>

I have used a foreach loop and access it that worked, but I want to access a single element in the value array. so I believe that using an alternate method would be better.

I have accessed questions[] by:

$q = $_POST['questions'];
echo $q[0];

but I tried to access choice[] and value[] in a similar way, but without success.

Firstly I tried print_r() to see how the array was set up, I saw i needed extra [] for choice and two extra for value, but I added them and got the error message, Undefined offset: 0, which from research I have found means that array is not set, I am obviously accessing it incorrectly, can someone please advise.

Also advice on a good tutorial for multi-dimensional arrays can be found would be appreciated, ive already looked at php.net.

Answer 1

Instead of telling you exact answer, let me guide you with the hint so that you can learn and get the fun yourself.

use:

    print_r($_POST);

with the result you'll be able to decide how to call each element. If you still have problem just comment below.

Answer 2

I think this would be easier to process via php than your current structure

<input name='questions[q1]' type='text' value='question 1' /><br/>
<input name='questions[choice][1]' type='text' value='option 1' />   
<input name='questions[value][1]' type='text' value='value' /><br/>
<input name='questions[choice][2]' type='text' value='option 1' />   
<input name='questions[value][2]' type='text' value='value' /><br/>  
<input name='questions[choice][3]' type='text' value='option 1' />   
<input name='questions[value][3]' type='text' value='value' /><br/>

i can see a few variations on this depending on your particular circumstances.

Answer 3

Basically this is how PHP will populate the array (*$_GET/$_POST -- depending on the form method*) when this form is submitted. Anything inside of the square brackets is literal (with the exception of a few characters like under-scores, which are translated to dashes). Empty brackets means PHP will automatically append each value to that array (starting from a 0 index) as if you used array_push in PHP.

So your array would like this...

$_POST['value']['1-1'][1][0] = 'whatever value the user supplied 1';
$_POST['value']['1-1'][2][0] = 'whatever value the user supplied 2';
$_POST['value']['1-1'][3][0] = 'whatever value the user supplied 3';

To access any of those elements in PHP you would use that same notation. If you wanted to iterate over them you'll have to consider that they are three dimensional. So for example...

foreach ($_POST['value']['1-1'] as $values) {
    foreach ($values as $value) {
        echo "$value\n";
    }
}

This would output

whatever value the user supplied 1
whatever value the user supplied 2
whatever value the user supplied 3

Also, I forgot to mention that you can use something like var_dump($_POST, $_GET); to look at a printable the structure of the array. I highly recommend var_dump for debugging variables, because it gives you a lot of useful information about those variables that goes above and beyond any other function like print_r/echo/etc...