array_shift()¶
array_shift() is a PHP native function that removes and returns the first element of an array. All numeric keys are re-indexed starting from zero; string keys are unaffected.
The operation is O(n) because all remaining numeric keys must be renumbered after the removal. This makes it slower than array_pop(), which removes the last element in O(1).
Together with array_push() or the [] append operator, array_shift() enables a FIFO queue pattern.
<?php
$array = [1, 2, 3, 4, 5];
echo array_shift($array); // 1
// $array == [2, 3, 4, 5];
$array = ['a' => 'x', 0 => 'y', 1 => 'z'];
echo array_shift($array); // x
// $array == [0 => 'y', 1 => 'z'];
?>
Related : array_unshift(), array_pop(), array_push(), array_splice(), First In, First Out (FIFO), Queue
