How to add array in front of array in php

PHP is a popular scripting language commonly used for web development. In PHP, arrays are a very common data type, and we often need to operate and process arrays. Sometimes, we need to add an array in front of the array, so how to achieve it? This article will explain how to add an array in front of an array in PHP and provide some sample code.

1. Use the " " operator to merge arrays

There is an operator " " in PHP, which can be used to merge two arrays into a new array. If two arrays have the same key name, the first array will be used and the value in the second array will be ignored. This method adds one array to the end of another array, thereby achieving the effect of adding an array in front of the array.

The sample code is as follows:

$array1 = array("a" => "apple", "b" => "banana");
$array2 = array("c" => "car", "d" => "dog");
$new_array = $array2 + $array1;
print_r($new_array);

The output result is:

Array
(
    [c] => car
    [d] => dog
    [a] => apple
    [b] => banana
)

2. Use the array_merge function to merge arrays

There is also an array_merge function in PHP. It is also possible to merge two arrays into a new array. This function works similarly to the " " operator, but with some differences. If the key names of two arrays are the same, the element values ​​in the second array will overwrite the element values ​​in the first array.

The sample code is as follows:

$array1 = array("a" => "apple", "b" => "banana");
$array2 = array("c" => "car", "b" => "book");
$new_array = array_merge($array2, $array1);
print_r($new_array);

The output result is:

Array
(
    [c] => car
    [b] => banana
    [a] => apple
)

In this example, the key name "b" in the second array covers the first array The key name "b" in , so the value is "banana". If you want to force the first array's values ​​to overwrite the second array's values, you can place the first array after the second array.

3. Use the array_unshift function

There is also an array_unshift function in PHP, which can add one or more elements in front of the array. This function inserts a new element at the beginning of the array and pushes existing elements backwards. This method can add an array in front of another array, thereby achieving the effect of adding an array in front of the array.

The sample code is as follows:

$array1 = array(1, 2, 3);
$array2 = array(4, 5, 6);
array_unshift($array1, $array2);
print_r($array1);

The output result is:

Array
(
    [0] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
        )

    [1] => 1
    [2] => 2
    [3] => 3
)

4. Use the array_splice function

There is also an array_splice function in PHP, which can be used in arrays Insert an element anywhere. This function can delete any element in the array and then insert the specified element into the array at the specified position. This method can add an array in front of another array, thereby achieving the effect of adding an array in front of the array.

The sample code is as follows:

$array1 = array("a" => "apple", "b" => "banana");
$array2 = array("c" => "car", "d" => "dog");

// 将数组 $array2 添加到数组 $array1 前面
array_splice($array1, 0, 0, $array2);
print_r($array1);

The output result is:

Array
(
    [0] => Array
        (
            [c] => car
            [d] => dog
        )

    [1] => apple
    [2] => banana
)

In this example, the array_splice function is used to delete 0 elements starting from position 0 in the array $array1 , and then insert array $array2 into array $array1 at position 0.

Summary:

The above are several methods of adding arrays in front of arrays. Which method to choose depends on your specific needs. If you just want to add an array in front of another array, you can use the " " operator or the array_merge function. If you want to add an element at any position in the array, you can use the array_unshift function or the array_splice function. I hope this article helps you better understand array operations in PHP.

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