HH\Lib\C\pop_back

Removes the last element from a Container and returns it

namespace HH\Lib\C;

function pop_back<T as Container<Tv>, Tv>(
  inout T $container,
): ?Tv;

If the Container is empty, null will be returned.

When an immutable Hack Collection is passed, the result will be defined by your version of hhvm and not give the expected results.

For non-empty Containers, see pop_backx. To get the first element, see pop_front.

Time complexity: O(1 or N) If the operation can happen in-place, O(1) if it must copy the Container, O(N). Space complexity: O(1 or N) If the operation can happen in-place, O(1) if it must copy the Container, O(N).

Parameters

• inout T $container

Returns

• ?Tv

Examples

$strings = vec["a", "b"];
$pop_back_result_1 = C\pop_back(inout $strings);
echo "First pop_back result: $pop_back_result_1\n";
//Output: First pop_back result: b

$empty_strings = vec[];
$pop_back_result_2 = C\pop_back(inout $empty_strings);
$pop_back_result_2_as_string = $pop_back_result_2 ?? "null";
echo "Second pop_back result: $pop_back_result_2_as_string\n";
//Output: Second pop_back result: null