$ var [] = array（）和$ var = array（）之间有什么区别？

Question

When I wrote $var = array('index' => 'some value') , it showed me an error when displaying a form on a page on the browser:

Notice: Undefined offset: 0 in C:\\xampp\\htdocs\\learn\\php\\admin\\authors\\form.html.php on line 28.

But when I wrote it like this $var[] = array('index' => 'some value') , it showed the page perfectly. So I have to put [] after variable name. In my knowledge, I can create an array variable like this $var = array(some array) .

So actually what is the difference between those two?

Answer 1

When you wrote $var = array('index' => 'some value'), you can't access $var[0], cause this index doesn't exist. You have to use $var['index'] to access the value.

Using $var[] = array(..), you push array() into $var, so it's create a new entry with index 0. If you use var_dump($var), you will have :

array([0] => array(['index'] => 'somevalue'));

Answer 2

The results are different:

$var = array('index' => 'some value');
var_dump($var);

// array(1) {
//   ["index"]=>
//   string(10) "some value"
// }

$var[] = array('index' => 'some value');
var_dump($var);

// array(1) {
//   [0]=>
//   array(1) {
//     ["index"]=>
//     string(10) "some value"
//   }
// }

If you look closely, the first example creates an associative array with one key pair. The second example creates an array that contains one item at index 0; that one item being the associative array.

Answer 3

If you do.. $var[]=array();

An empty array is stored as the first index inside the $var array..

Array
(
    [0] => Array
        (
        )

)

If you do.. $var = array();

You are just declaring it $var as an array.

Array
(
)

So obviously, you know what the difference is...

A simple demo

Answer 4

$var[] = array() is a two dimensional array its like saying.

 $var = array(); // 1 dimensional array
 $var[0] = array();

try using var_export($var) in your two different examples to see the difference.

Answer 5

$var = array('index' => 'some value') means a variable with an array value inside

$var[] = array('index' => 'some value') means an array with another array in the last index. This is the same of write $var = array(array('index' => 'some value'))