What are the classifications of arrays in php?

There are four classifications of arrays in PHP, which are: 1. Index array, the most common and basic array type; 2. Associative array, by specifying a custom key name or string as an index. Stores data; 3. Multidimensional arrays, nesting another array within an array; 4. Binary arrays, allowing binary data to be manipulated directly without conversion like strings.

The operating system of this tutorial: Windows10 system, PHP version 8.1.3, DELL G3 computer.

In PHP, array is a very important data type used to store and operate a set of related data. According to the different characteristics and uses of arrays, arrays can be divided into the following categories.

1. Index Array:

Index array is the most common and basic array type. This type of array uses integers as indexes and stores data in a certain order. The index starts from 0 and increases, and each element is accessed through the corresponding index. For example:

$colors = array('red', 'green', 'blue');
echo $colors[0]; // 输出 red
echo $colors[2]; // 输出 blue

2. Associative Array:

Associative array stores data by specifying a custom key name or string as an index. Each element consists of a key and a value, rather than being indexed numerically. For example:

$student = array('name' => 'John', 'age' => 20, 'major' => 'Computer Science');
echo $student['name']; // 输出 John
echo $student['age']; // 输出 20

3. Multidimensional Array:

Multidimensional array refers to nesting another array within an array. It can be a combination of an indexed array or an associative array. A two-dimensional, three-dimensional or higher-dimensional data structure is formed. For example:

$products = array(
array('name' => 'iPhone', 'price' => 999),
array('name' => 'iPad', 'price' => 799),
array('name' => 'MacBook', 'price' => 1299)
);
echo $products[0]['name']; // 输出 iPhone
echo $products[1]['price']; // 输出 799

4. Binary Array:

Binary array is a newer feature in PHP. It allows direct manipulation of binary data without the need for conversion like strings. By using the pack() and unpack() functions, binary data can be converted into an array and unpacked and packed when required. This type of array is typically used to handle network communications or file operations. For example:

$binary_data = pack('C*', 65, 66, 67);
$unpacked_data = unpack('C*', $binary_data);
print_r($unpacked_data);

Output:

Array
(
[1] => 65
[2] => 66
[3] => 67
)

These are common array classifications in PHP. For each array type, there are applicable scenarios and operation methods. Developers can choose the appropriate array type to store and process data based on specific needs.

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