Discuss various methods of array merging in PHP

With the rapid development of Web development, the operation of PHP arrays has become more and more important. From processing form data to dynamically generating web page content, PHP arrays enable developers to handle a variety of data with ease. Merging arrays is one of the most basic operations in PHP. In actual development, we usually need to merge two or more arrays into one to better manage and operate data. In this article, we will discuss various methods of array merging in PHP.

Method 1: array_merge function

The array_merge function is one of the most commonly used functions to merge arrays in PHP. It can combine two or more arrays into a new array.

Syntax: array array_merge ( array $array1 [, array $array2 [, array $... ]] )

The array_merge function accepts any number of arrays as parameters and returns a new array , which contains all elements in the input array. Note that the array_merge function does not merge arrays recursively. If the input arrays have the same key name, later values ​​will overwrite previous values.

The following is an example:

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
print_r($result);

Output result:

Array ( [color] => green [0] => 2 [1] => 4 [2] => a [3] => b [shape] => trapezoid [4] => 4 )

In this example, "color" in $array2 overwrites "color" in $array1, And "4" repeats the value in $array1.

Method 2:

You can also use the " " operator to merge arrays. This essentially concatenates two arrays into a new array.

The following is an example of using the " " operator:

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = $array1 + $array2;
print_r($result);

Output result:

Array ( [color] => red [0] => 2 [1] => 4 [2] => a [3] => b [shape] => trapezoid [4] => 4 )

In this example, "color" in $array1 is retained as the original value, The "color" in $array2 is discarded. At the same time, duplicate values ​​will also be discarded.

It should be noted that the use of the " " operator is limited to arrays with integer key names. This method will not work if the key name is a string. Even if the key name is an integer, if there are duplicate keys, the later keys will overwrite the previous keys.

Method 3: array_replace function

The array_replace function can merge one or more arrays into a new array while retaining the last value of each key.

Syntax: array array_replace (array $array1 [, array $array2 [, array $... ]] )

The following is an example:

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_replace($array1, $array2);
print_r($result);

Output results:

Array ( [color] => green [0] => a [1] => b [2] => 4 [shape] => trapezoid )

In this example, the last value of "color" is the "color" value in $array2, and the last value of "4" is also the value in $array2. Note that array_replace does not re-index the resulting array, but merges it based on the key name.

Method 4: array_merge_recursive function

The array_merge_recursive function is a variant of the array_merge function, which recursively merges all elements with the same key name into an array. If the values ​​corresponding to the same key in two arrays are arrays, the arrays will be merged recursively.

The following is an example:

$array1 = array("color" => array("favorite" => "red"), 2, 4);
$array2 = array("color" => array("favorite" => "green"), "shape" => "trapezoid", 4);

$result = array_merge_recursive($array1, $array2);
print_r($result);

Output result:

Array ( [color] => Array ( [favorite] => Array ( [0] => red [1] => green ) ) [0] => 2 [1] => 4 [shape] => trapezoid )

In this example, the value of the "color" key name is an associative array, not a simple value. Therefore, when using array_merge_recursive, the values ​​will be merged recursively, not just simply merged.

To sum up, these are four ways to merge arrays in PHP. array_merge() is the most commonly used method, but you can choose other methods that suit your specific needs. array_merge_recursive is the best choice when you need to merge associative arrays recursively. Therefore, when writing PHP code, it is necessary to understand the different methods of merging arrays for better management and manipulation of data.

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