PHP array_shift Function

last modified March 13, 2025

The PHP array_shift function removes and returns the first element of an array. It’s useful for queue-like operations where you need FIFO behavior.

Basic Definition

The array_shift function extracts the first element from an array. All numerical array keys are re-indexed starting from 0 after the operation.

Syntax: array_shift(array &$array): mixed. The function modifies the original array and returns the shifted value. Returns null if array is empty.

Basic array_shift Example

This demonstrates the fundamental usage of array_shift to remove the first element from an array.

basic_array_shift.php

<?php

$fruits = [‘apple’, ‘banana’, ‘cherry’]; $firstFruit = array_shift($fruits);

echo “Removed: $firstFruit\n”; print_r($fruits);

This removes ‘apple’ from the array and returns it. The remaining elements are re-indexed starting from 0. The original array is modified.

Using array_shift in a Loop

Process array elements one by one using array_shift in a loop.

loop_array_shift.php

<?php

$tasks = [’task1’, ’task2’, ’task3’];

while (!empty($tasks)) { $currentTask = array_shift($tasks); echo “Processing: $currentTask\n”; }

// Processing: task1 // Processing: task2 // Processing: task3

This processes each task in order, removing them from the array as they’re processed. The loop continues until the array is empty.

Handling Empty Arrays

array_shift returns null when called on an empty array.

empty_array.php

<?php

$emptyArray = []; $result = array_shift($emptyArray);

var_dump($result);

When the array is empty, array_shift returns null without modifying the array. This behavior is useful for error handling.

Preserving Associative Keys

array_shift only re-indexes numerical keys, preserving string keys.

associative_array.php

<?php

$user = [ ’name’ => ‘John’, ‘age’ => 30, 0 => ‘admin’ ];

$firstValue = array_shift($user);

echo “Removed: $firstValue\n”; print_r($user);

The numerical key (0) is removed while string keys remain unchanged. The function only re-indexes numerical array keys.

Combining with array_push for Queue

Implement a simple queue using array_shift and array_push.

queue_implementation.php

<?php

$queue = [];

// Enqueue items array_push($queue, ‘item1’); array_push($queue, ‘item2’);

// Dequeue items $firstItem = array_shift($queue); echo “Processed: $firstItem\n”;

$secondItem = array_shift($queue); echo “Processed: $secondItem\n”;

This demonstrates a FIFO (First-In-First-Out) queue. Items are added to the end and removed from the front, maintaining proper queue order.

Best Practices

• Performance: Avoid on large arrays as re-indexing is O(n).

• Error Handling: Check array isn’t empty before shifting.

• Alternatives: Consider SplQueue for better performance.

• Memory: Be aware it modifies the original array.

Source

PHP array_shift Documentation

This tutorial covered the PHP array_shift function with practical examples showing its usage for array manipulation scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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