Deleting an element from an array in PHP
arrays, php, unset
Solution
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 single array element you can use `unset()` and alternatively `array_splice()`.
By key or by value?
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 doesn't occur more than once, since `array_search()` returns the first hit only.
`unset()` Expression
Note: 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 (the array remains a list).
Example Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
unset($array[1]);
// ↑ Key of element to delete
Example Output:
[
[0] => a
[2] => c
]
`array_splice()` Function
If you use `array_splice()` the (integer) keys will automatically be reindex-ed, but the associative (string) keys won't change — as opposed to `array_values()` after `unset()`, which will convert all keys to numerical keys.
Note: `array_splice()` needs the offset, not the key, as the second parameter; offset `= array_flip(array_keys(`array`))[`key`]`.
Example Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
array_splice($array, 1, 1);
// ↑ Offset of element to delete
Example Output:
[
[0] => a
[1] => c
]
`array_splice()`, same as `unset()`, take the array by reference. You don’t assign the return values 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 to remove from the array.
`array_diff()` Function
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.
Example Code:
$array = [0 => "a", 1 => "b", 2 => "c", 3 => "c"];
$array = array_diff($array, ["a", "c"]);
// └────────┘
// Array values to delete
Example Output:
[
[1] => b
]
`array_diff_key()` Function
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.
Example Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
$array = array_diff_key($array, [0 => "xy", "2" => "xy"]);
// ↑ ↑
// Array keys of elements to delete
Example 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.
`array_filter()` Function
If you want to delete all elements with a specific value in the array you can use `array_filter()`.
Example Code:
$array = [0 => "a", 1 => "b", 2 => "c"];
$array = array_filter($array, static function ($element) {
return $element !== "b";
// ↑
// Array value which you want to delete
});
Example Output:
[
[0] => a
[2] => c
]
Problem
Is there an easy way to delete an element from an array using PHP, such that `foreach ($array)` no longer includes that element? I thought that setting it to `null` would do it, but apparently it does not work.