The array_shift() function in PHP is used to remove the first element from an array and return it. The array keys are re-indexed after the shift, and the array is modified in place.

Syntax:

array_shift(array &$array): mixed

• $array: The input array, passed by reference.
• Return value: The first element of the array, or NULL if the array is empty.

Example 1: Basic usage

$array = [1, 2, 3, 4, 5];
$shifted = array_shift($array);

echo "Shifted element: " . $shifted . "\n"; // Output: 1
print_r($array); // Output: [2, 3, 4, 5]

In this example:

• The first element (1) is removed from the $array.
• The shifted element (1) is returned.
• The remaining array becomes [2, 3, 4, 5].

Example 2: With an associative array

$array = ["a" => "apple", "b" => "banana", "c" => "cherry"];
$shifted = array_shift($array);

echo "Shifted element: " . $shifted . "\n"; // Output: apple
print_r($array); // Output: Array ( [b] => banana [c] => cherry )

• The first element (apple) is removed.
• The remaining array has re-indexed keys (b and c).

Example 3: Empty array

$array = [];
$shifted = array_shift($array);

echo "Shifted element: " . ($shifted ? $shifted : "None") . "\n"; // Output: None

• When the array is empty, array_shift() returns NULL.

Example 4: Working with numeric keys

$array = [10, 20, 30, 40];
$shifted = array_shift($array);

echo "Shifted element: " . $shifted . "\n"; // Output: 10
print_r($array); // Output: [20, 30, 40]

• The first element (10) is removed, and the array is re-indexed.

Key Points:

• The array is modified directly (passed by reference).
• The array keys are re-indexed after the shift, so the keys of remaining elements are adjusted accordingly.
• The function returns the value of the shifted element or NULL if the array is empty.