You have asked two questions that are not quite equivalent:
- Firstly, how to determine whether an array has only numeric keys
- Secondly, how to determine whether an array has sequential numeric keys, starting from 0
Consider which of these behaviours you actually need. (It may be that either will do for your purposes.)
The first question (simply checking that all keys are numeric) is answered well by Captain kurO.
For the second question (checking whether the array is zero-indexed and sequential), you can use the following function:
function isAssoc(array $arr)
{
if (array() === $arr) return false;
return array_keys($arr) !== range(0, count($arr) - 1);
}
var_dump(isAssoc(['a', 'b', 'c'])); // false
var_dump(isAssoc(["0" => 'a', "1" => 'b', "2" => 'c'])); // false
var_dump(isAssoc(["1" => 'a', "0" => 'b', "2" => 'c'])); // true
var_dump(isAssoc(["a" => 'a', "b" => 'b', "c" => 'c'])); // true
There are different ways to delete an array element, where some are more useful for some specific tasks than others.
Deleting a single array element
If you want to delete just one array element you can use unset() or alternatively \array_splice().
If you know the value and don’t know the key to delete the element you can use \array_search() to get the key. This only works if the element does not occur more than once, since \array_search returns the first hit only.
Note that when you use unset() the array keys won’t change. If you want to reindex the keys you can use \array_values() after unset(), which will convert all keys to numerically enumerated keys starting from 0.
Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
unset($array[1]);
// ↑ Key which you want to delete
Output:
[
[0] => a
[2] => c
]
If you use \array_splice() the keys will automatically be reindexed, but the associative keys won’t change — as opposed to \array_values(), which will convert all keys to numerical keys.
\array_splice() needs the offset, not the key, as the second parameter.
Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
\array_splice($array, 1, 1);
// ↑ Offset which you want to delete
Output:
[
[0] => a
[1] => c
]
array_splice(), same as unset(), take the array by reference. You don’t assign the return values of those functions back to the array.
Deleting multiple array elements
If you want to delete multiple array elements and don’t want to call unset() or \array_splice() multiple times you can use the functions \array_diff() or \array_diff_key() depending on whether you know the values or the keys of the elements which you want to delete.
If you know the values of the array elements which you want to delete, then you can use \array_diff(). As before with unset() it won’t change the keys of the array.
Code:
$array = [0 => "a", 1 => "b", 2 => "c", 3 => "c"];
$array = \array_diff($array, ["a", "c"]);
// └────────┘
// Array values which you want to delete
Output:
[
[1] => b
]
If you know the keys of the elements which you want to delete, then you want to use \array_diff_key(). You have to make sure you pass the keys as keys in the second parameter and not as values. Keys won’t reindex.
Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
$array = \array_diff_key($array, [0 => "xy", "2" => "xy"]);
// ↑ ↑
// Array keys which you want to delete
Output:
[
[1] => b
]
If you want to use unset() or \array_splice() to delete multiple elements with the same value you can use \array_keys() to get all the keys for a specific value and then delete all elements.
Best Answer