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:

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:

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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