How to use array_merge function to merge arrays in PHP

In PHP, array operations are a very frequent operation. When we need to use values ​​from multiple arrays at the same time, we need to merge these arrays into one array for easy operation. PHP provides the array_merge function to merge two or more arrays into one array. In this article, we will explain how to merge arrays using the array_merge function.

The syntax of the array_merge function is as follows:

array array_merge ( array $array1 [, array $... ] )

Among them, array1 must be an array, ... represents optional parameters, and you can pass multiple array. This function combines the arrays in all arguments into a new array and returns that array.

For example, the following code merges two arrays and saves the result in a new array:

$array1 = array('apple', 'banana', 'orange');
$array2 = array('watermelon', 'pear', 'pineapple');
$result = array_merge($array1, $array2);

print_r($result);

The output result is:

Array
(
    [0] => apple
    [1] => banana
    [2] => orange
    [3] => watermelon
    [4] => pear
    [5] => pineapple
)

From the output result, you can It can be seen that the array_merge() function merges the two arrays into a new array and re-indexes the array in increasing order.

In addition to the default behavior used in the above example, the array_merge() function has some other parameter settings:

1. Keep key name

By default, the array_merge() function will re-index the numeric key names in the array. If you want to retain the key names of the array, you can set the first parameter of the array_merge() function (array1) to an associative array.

For example, the following code will retain the key names and merge two associative arrays:

$array1 = array('a' => 'apple', 'b' => 'banana');
$array2 = array('c' => 'carrot', 'd' => 'date');
$result = array_merge($array1, $array2);

print_r($result);

The output result is:

Array
(
    [a] => apple
    [b] => banana
    [c] => carrot
    [d] => date
)

As you can see, array_merge( )The function merges two associative arrays into one associative array and retains the original key names.

2. Merge numeric key names

array_merge()The function only merges the values ​​of numeric key names by default. If you need to merge the values ​​of associative arrays, you can Use the operator to merge.

For example, the following code merges associative arrays and numeric arrays:

$array1 = array('a' => 'apple', 'b' => 'banana');
$array2 = array('c' => 'carrot', 'd' => 'date');
$result = $array1 + $array2;

print_r($result);

The output result is:

Array
(
    [a] => apple
    [b] => banana
    [c] => carrot
    [d] => date
)

As you can see, $array1 $array2 Implemented the operation of merging two arrays into an associative array and retaining key names.

Summary: array_merge()The function is a very commonly used function in PHP, which can merge two or more arrays and return a new array. When merging arrays, you can retain the original key names and use the operator to merge associative arrays. Mastering the usage of the array_merge() function is very important for PHP array operations.

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