PHP numeric array order

问题:

I have an array and want to create a new numeric array. This looks like this:

$created_old = explode("_", $result[$i]["created"]);
$created_new = array();
$created_new[0] = $created_old[2];
$created_new[1] = $created_old[0];
$created_new[2] = $created_old[1];
$created_new[3] = "";
$created_new[4] = rtrim(explode(":", $created_old[3])[2], ")");

//Get name from the database

$created_new[3] = $name;

$created = implode("_", $created_new);

This version works just fine, but the previous was missing one line, so the code would be this:

$created_old = explode("_", $result[$i]["created"]);
$created_new = array();
$created_new[0] = $created_old[2];
$created_new[1] = $created_old[0];
$created_new[2] = $created_old[1];
//$created_new[3] = ""; - I am missing
$created_new[4] = rtrim(explode(":", $created_old[3])[2], ")");

//Get name from the database

$created_new[3] = $name;

$created = implode("_", $created_new);

In the second code the string $created is in the wrong order. The index 4 and 3 are switched. If it would be an associative array I would understand this but as it is an numeric array I assume the indices to increase numerically and beeing ordered like this. As I have a working version I do not need help to fix this code but rather understand why the code behaves as it does...

Best regards JRsz

回答1:

All PHP arrays are associative. There's no such thing as a "numeric array" expect in colloquial speech. A key can be either a string or a number, it doesn't matter. Keys are still ordered by their order of insertion and never implicitly ordered by their value. You would not be surprised by this behaviour I assume:

$arr['a'] = 1;
$arr['c'] = 3;
$arr['b'] = 2;
// ['a' => 1, 'c' => 3, 'b' => 2]

The exact same mechanics are at work in your "numeric array".

If you want to sort your keys, you need to do so explicitly using ksort.