Definition and Usage

PHP Version
4+

The array_shift() function removes the first element from an array and returns it.

Features

  • Removes the first element from an array.
  • Directly modifies the original array.
  • This operation decreases the length of the array by one
  • Returns the removed element.

Basic Example

PHP 
$array = ['orange', 'banana', 'apple'];

// Removes the first element from the array
array_shift($array);
print_r($array);
/*
Output:
    Array
    (
        [0] => banana
        [1] => apple
    )
*/

The array_pop() function is similar to array_shift() , but it removes the last element from an array.

Syntax

PHP 
array_shift(array &$array): mixed

Parameters

Parameters of the array_shift() Function
&$array The target array from which the first element will be removed (passed by reference).

Return Values

The array_shift() function returns the first element removed from the array. If the array is empty and there is no element to remove, it returns null.

PHP Return Value of array_shift() 
// Initialize the array
$array = ['orange', 'banana', 'apple'];

// Remove the first element from the array
$removedItem = array_shift($array);
print_r($array);
/*
Output:
    Array
    (
        [0] => banana
        [1] => apple
    )
*/

echo $removedItem; // Output: 'orange'

// Empty array
$emptyArray = [];
$emptyArray_removedItem = array_shift($emptyArray); // Array is empty, no element to remove

var_dump($emptyArray_removedItem); // Output: NULL

Important Notes and Use Cases

There are several key concepts and precautions to keep in mind when using the array_shift() function.

  1. Return Value
  2. Modification of the Original Array and Array Length
  3. Works with Associative Arrays
  4. Implementing a Queue
  5. Removing the First Element with unset()

Return Value

The array_shift() function returns the removed element. You can store the returned value in a variable.

PHP 
$fruits = ['apple', 'banana', 'cherry'];
$removedFruit = array_shift($fruits);
echo $removedFruit; // Output: 'apple'

Modification of the Original Array and Array Length

The array_shift() function modifies the original array. Therefore, when you remove an element, the array changes and its length decreases.

PHP 
$fruits = ['apple', 'banana', 'cherry'];
array_shift($fruits);
echo count($fruits); // Output: 2

Works with Associative Arrays

The array_shift() function works not only with indexed arrays but also with associative arrays. Since it removes and returns the first element, it is not restricted by array type.

PHP 
$assocArray = ['name' => 'John', 'age' => 30];
array_shift($assocArray);
print_r($assocArray);
/*
Output:
    Array
    (
        [age] => 30
    )
*/

Implementing a Queue

You can use the array_shift() function to treat an array as a queue. It is useful for removing and processing the first element in the queue.

The following example demonstrates a simple queue implementation that processes array elements using array_shift(). This code can be used to simulate a basic web application that processes incoming requests.

PHP 
// Create an initial request queue
$requestQueue = [];

// Add requests to the queue
$requestQueue[] = 'Request 1';
$requestQueue[] = 'Request 2';
$requestQueue[] = 'Request 3';

// Process requests
while ($request = array_shift($requestQueue)) {
    // Process the request
    echo "Processing: $request";

    // Simulate a random processing time
    $processingTime = rand(1, 3);
    sleep($processingTime); // Wait for simulated processing time

    echo "Completed: $request";
}

// Code to run after all requests have been processed
echo "All requests have been processed";

Removing the First Element with unset()

Instead of using array_shift(), you can remove the first element of an array using the unset(). The unset() language construct destroys the specified variable.

PHP 
// Original array
$fruits = ['apple', 'banana', 'cherry'];

// Remove the first element using unset()
unset($fruits[0]);

// Output the array
print_r($fruits);
/*
Output:
    Array
    (
        [0] => banana
        [1] => cherry
    )
*/

Using unset() to remove specific elements from an array requires caution, and is therefore not recommended. If you remove an element from the middle of an array (instead of the first or last element), the index remains empty, and PHP does not reindex the array automatically.

References

See also