PHP array_unshift() Function
Quick summary: The PHP array_unshift() function prepends one or more elements to the beginning of an array.
PHP array_unshift() Syntax
array_unshift(array &$array, mixed ...$values): intPHP
PHP array_unshift() Basic examples
$array = [2,3];
array_unshift($array, 1);
print_r($array);PHP
Output:
Array ( [0] => 1 [1] => 2 [2] => 3 )Adds element to the beginning and reindexes numeric keys.
PHP array_unshift() Real-world usage
$queue = ['task2','task3'];
array_unshift($queue,'task1');
print_r($queue);PHP
Output:
Array ( [0] => task1 [1] => task2 [2] => task3 )Add priority item at the start of a queue.
PHP array_unshift() Edge cases
$array=[];
$count=array_unshift($array,'a');
var_dump($count);PHP
Output:
int(1)Returns new number of elements.
PHP array_unshift() Common mistakes
Expecting keys to be preserved
Numeric keys are reindexed.
Incorrect
$a=[10=>1,20=>2]; array_unshift($a,0);Correct
// Use array_merge() if key preservation is requiredarray_unshift() reindexes numeric keys.
PHP array_unshift() Frequently Asked Questions
What does array_unshift() do?
Prepends one or more elements to the beginning of an array.
Use case?
Queue operations.
Return value?
New array length.
Modifies array?
Yes.
Common mistake?
Reindexing numeric keys.
Performance?
Slower on large arrays.
Supports multiple values?
Yes.
Safe?
Yes.
Alternative?
array_merge().
Handles empty array?
Yes.
Used in stacks?
Yes.
Best practice?
Avoid on large datasets.