The difference between php array and spl array

With the development of web development technology, PHP has become one of the most commonly used server-side programming languages. In PHP programming, arrays are a very important data type used to store multiple variables or values. In PHP, there are two types of arrays: ordinary arrays and SPL (Standard PHP Library, Standard PHP Library) arrays. This article will introduce the differences between these two arrays.

1. Basic definition

Ordinary array is PHP's built-in array. It can be declared in code through the array() function or [] and supports multiple data types. Elements. For example:

$numbers = array(1, 2, 3); $fruits = ['apple', 'orange', 'banana']; $people = array( 'Tom' => 30, 'Jane' => 25, 'Dave' => 42 );

SPL array is an array implemented using the SPL library and must first be declared and initialized through a class in the SPL library. For example:

$numbers = new SplFixedArray(3); $numbers[0] = 1; $numbers[1] = 2; $numbers[2] = 3; $people = new SplObjectStorage(); $person1 = new stdClass(); $person1->name = 'Tom'; $people->attach($person1, ['age' => 30]);

As can be seen from the above sample code, ordinary arrays need to be defined using the array() function or [], while SPL arrays need to be defined with the help of classes in the SPL library. In addition, SPL arrays support some specific methods, as described below.

2. Array size

The size of an ordinary array can be dynamically adjusted, and elements can be added or deleted at any time:

$numbers = array(1, 2, 3); $numbers[] = 4; // 添加一个元素 unset($numbers[1]); // 删除一个元素

The size of the SPL array is determined when it is created. It has been determined and cannot be changed. This means that once the array size is defined, elements cannot be added or removed:

$numbers = new SplFixedArray(3); $numbers[0] = 1; $numbers[1] = 2; $numbers[2] = 3; $numbers[3] = 4; // 报错，无法添加元素 unset($numbers[1]); // 报错，无法删除元素

Since SPL arrays are already fixed in size, they are faster when accessed.

3. Array operations

The operations of ordinary arrays are similar to arrays in other languages. For example, you can use the array_push(), array_pop(), array_shift(), and array_unshift() functions to add or remove elements to the end or beginning of an array:

$numbers = array(1, 2, 3); array_push($numbers, 4); // 在数组末尾添加一个元素 array_pop($numbers); // 从数组末尾删除一个元素 array_unshift($numbers, 0); // 在数组开头添加一个元素 array_shift($numbers); // 从数组开头删除一个元素

SPL arrays also support similar operations, but you need to use specific Methods. For example, you can use the add() and setSize() methods in the SplFixedArray class to add and set the size:

$numbers = new SplFixedArray(3); $numbers[0] = 1; $numbers[1] = 2; $numbers[2] = 3; $numbers->add(4); // 在数组末尾添加一个元素 $numbers->setSize(4); // 手动设置数组大小

4. Iteration

Normal arrays can be iterated over using a foreach loop Elements in the array:

$fruits = ['apple', 'orange', 'banana']; foreach ($fruits as $fruit) { echo $fruit . ' '; }

SPL arrays can be traversed using the SPL iterator. SPL iterators provide a unified interface for traversing various data structures. For example, you can use the current(), key() and next() methods in the SplFixedArrayIterator class to traverse the SPL array:

$numbers = new SplFixedArray(3); $numbers[0] = 1; $numbers[1] = 2; $numbers[2] = 3; $iterator = new SplFixedArrayIterator($numbers); foreach ($iterator as $key => $value) { echo $key . '=>' . $value . ' '; }

As can be seen from the above example, the SPL array needs to be iterated using the SPL iterator , instead of using the foreach loop directly.

5. Performance

SPL arrays are faster than normal arrays when processing a large number of elements. This is because SPL arrays are implemented using optimized code written in C language, while ordinary arrays are implemented by the PHP language itself. Additionally, the elements of an SPL array must be of the same data type, so they are more efficient in memory allocation and use.

In general, ordinary arrays are suitable for storing variable-sized element lists, while SPL arrays are suitable for element lists that require fixed size and high performance. Which array to use depends on the developer's specific needs.

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