Explore different approaches to PHP array deep copying: performance, pros and cons

In PHP, you can use the array_merge_recursive(), json_encode()/json_decode() and clone methods to copy an array. array_merge_recursive() recursively merges nested arrays, but is slower; json_encode()/json_decode() is faster, but consumes memory; clone is the fastest, but only works on objects (including arrays).

Explore different methods of array deep copying in PHP: performance, advantages and disadvantages

Introduction

In PHP, copying an array is a common operation. However, the default assignment operator does not create a copy of the array, but creates a reference to the original array. In some cases, this can lead to unintended consequences. Therefore, it is important to understand the different methods of deep copying arrays in PHP and their pros and cons.

Method 1: array_merge_recursive()

array_merge_recursive() The function will merge multiple arrays into a new array and merge them recursively. Any nested array. It can be used to create a deep copy of an array.

$original = ['key1' => 'value1', 'key2' => ['subkey1' => 'subvalue1']];
$copy = array_merge_recursive([], $original);

Advantages:

• Simple and easy to use.
• Recursively merge nested arrays.

Disadvantages:

• Slower than other methods.
• May cause stack overflow errors if the array is too nested.

Method 2: json_encode() and json_decode()

json_encode() The function converts a PHP variable to a JSON string , json_decode() function converts JSON string into PHP variable. We can use these functions to create a deep copy of an array.

$original = ['key1' => 'value1', 'key2' => ['subkey1' => 'subvalue1']];
$copy = json_decode(json_encode($original), true);

Advantages:

• is faster than array_merge_recursive().
• Handle arrays of any type.

Disadvantages:

• For large arrays, a lot of memory may be consumed.

Method 3: Using clone

Cloning objects also works with arrays as it creates a completely separate copy of the original array copy.

$original = ['key1' => 'value1', 'key2' => ['subkey1' => 'subvalue1']];
$copy = clone $original;

Advantages:

• The fastest deep copy method.
• Creates a true copy, disconnected from the original array.

Disadvantages:

• can only be used for objects (including arrays).

Practical Case

The following is a practical case that demonstrates how to use deep copy of a PHP array:

<?php

// 创建一个包含嵌套数组的原始数组
$original = [
    'name' => 'John',
    'age' => 25,
    'address' => [
        'street' => 'Main Street',
        'city' => 'Anytown'
    ]
];

// 创建使用不同方法的深度副本
$copy1 = array_merge_recursive([], $original);
$copy2 = json_decode(json_encode($original), true);
$copy3 = clone $original;

// 验证副本与原始数组是否不同
var_dump($copy1 !== $original); // 输出：true
var_dump($copy2 !== $original); // 输出：true
var_dump($copy3 !== $original); // 输出：true

In the above example , we create a primitive array containing nested arrays. We then created three deep copies using array_merge_recursive(), json_encode()/json_decode() and clone. Finally, we use var_dump() to verify that the copies are different from the original array, and the result is true, indicating that these copies are independent instances of the original array.

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