Use the PHP function "array_unshift" to insert elements to the beginning of the array

Use the PHP function "array_unshift" to insert an element at the beginning of the array

PHP is a widely used server-side scripting language for creating dynamic web pages. In PHP, an array is a very important data structure used to store and manipulate a set of data. Sometimes we need to insert an element at the beginning of the array, then we can use the PHP built-in function "array_unshift".

The "array_unshift" function is to insert one or more elements into the beginning of the array and return the number of elements in the array after insertion. Its syntax is as follows:

array_unshift(array $array, mixed $value1 [, mixed $[value2 …]])

Among them, $array is the array to insert elements, $value1, $value2 is the element to be inserted.

The following is a simple example that demonstrates how to use the "array_unshift" function to insert elements to the beginning of the array:

<?php
$fruits = array("apple", "orange", "banana");
echo "Before array_unshift: ";
print_r($fruits);

array_unshift($fruits, "grape");
echo "After array_unshift: ";
print_r($fruits);
?>

Run the above code, the output is as follows:

Before array_unshift: Array
(
    [0] => apple
    [1] => orange
    [2] => banana
)
After array_unshift: Array
(
    [0] => grape
    [1] => apple
    [2] => orange
    [3] => banana
)

In this example, the initial array contains three fruits: apples, oranges and bananas. After inserting "grape" at the beginning of the array using the "array_unshift" function, the array becomes an array of four elements, with "grape" in the first position.

In addition to inserting one element, we can also use the "array_unshift" function to insert multiple elements at once. For example:

<?php
$numbers = array(3, 4, 5);
echo "Before array_unshift: ";
print_r($numbers);

array_unshift($numbers, 1, 2);
echo "After array_unshift: ";
print_r($numbers);
?>

Run the above code, the output is as follows:

Before array_unshift: Array
(
    [0] => 3
    [1] => 4
    [2] => 5
)
After array_unshift: Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

In this example, the initial array contains three numbers: 3, 4 and 5. After using the "array_unshift" function to insert 1 and 2 at the beginning of the array, the array becomes an array of five elements, with 1 and 2 in the first two positions.

To summarize, the PHP function "array_unshift" is a very convenient way to insert elements to the beginning of an array. It can be used to insert one or more elements without manually re-indexing the array. In actual projects, we can flexibly use this function to meet different needs.

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