PHP Array Deep Copy Tradeoffs: Choosing the Right Approach

Shallow copy only copies references, not values; deep copy creates an independent copy of the original array, including copying nested values. Shallow copy is suitable for quickly creating a copy, modifying the copy affects the original array, and does not copy nested values; deep copy is suitable for creating independent copies, copying nested values, and does not want to modify the copy to affect the original array. There are differences in speed, memory usage, and modification impact, and the choice depends on specific needs.

#PHP Array Deep Copy Trade-offs: Choosing the Right Approach

In PHP, array copying is one of the tasks that developers often need to perform. There are two main ways to copy an array: shallow copy and deep copy.

Shallow copyOnly copies the reference to the array, not the values ​​contained in the array. This means that any changes made to the shallowly copied array will also be reflected in the original array.

Deep Copy Creates a completely new copy of the original array. This includes copying all values ​​contained in the array, even if the values ​​themselves are other arrays or objects. This means that any changes made to the deep-copied array will not affect the original array.

When to use shallow copy

• When you just need to create a quick, simple copy
• When you don’t need to copy an embedded copy When copying values ​​in an array or object
• When you want changes to the copy to also affect the original array

When to use a deep copy

• When you need to create an independent copy of the original array
• When you need to copy the values ​​in a nested array or object
• When you don't want changes to the copy to affect the original array

Advantages of shallow copy

• Fast and simple
• Save memory

Disadvantages of shallow copy

• Changes to the copy will also affect the original array
• Does not copy values ​​in nested arrays or objects

Advantages of deep copy

• Create an independent copy of the original array
• Copy the values ​​in a nested array or object
• Pair copy Changes will not affect the original array

Disadvantages of deep copy

• Slower and more complex than shallow copy
• Take up More memory

Practical case

The following code example demonstrates the difference between shallow copy and deep copy:

// 浅复制
$originalArray = [
    'name' => 'John Doe',
    'age' => 30,
    'address' => [
        'street' => 'Main Street',
        'number' => 123
    ]
];

$shallowCopy = $originalArray;

$shallowCopy['name'] = 'Jane Doe'; // 浅复制：对副本的更改也影响原始数组
$originalArray['address']['street'] = 'New Main Street'; // 浅复制：对原始数组的更改也影响副本

var_dump($originalArray); // 输出：['name' => 'Jane Doe', 'age' => 30, 'address' => ['street' => 'New Main Street', 'number' => 123]]
var_dump($shallowCopy); // 输出：['name' => 'Jane Doe', 'age' => 30, 'address' => ['street' => 'New Main Street', 'number' => 123]]

// 深度复制
$deepCopy = json_decode(json_encode($originalArray), true);

$deepCopy['name'] = 'John Doe Jr.'; // 深度复制：对副本的更改不会影响原始数组
$originalArray['address']['number'] = 124; // 深度复制：对原始数组的更改不会影响副本

var_dump($originalArray); // 输出：['name' => 'John Doe', 'age' => 30, 'address' => ['street' => 'New Main Street', 'number' => 124]]
var_dump($deepCopy); // 输出：['name' => 'John Doe Jr.', 'age' => 30, 'address' => ['street' => 'New Main Street', 'number' => 123]]

Conclusion

Shallow copy and deep copy are both useful techniques in PHP. Which method you choose depends on your specific needs. Understanding their advantages and disadvantages can help you make informed decisions and avoid unexpected behavior.

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