The underlying implementation of php multidimensional array

With the development of the Internet era, the PHP language occupies a pivotal position in the Web. As one of the most commonly used data structures in the PHP language, multidimensional arrays have important application value in program development. This article will conduct an in-depth analysis of the underlying implementation of multi-dimensional arrays in PHP, hoping to provide readers with a deeper understanding.

1. Definition of multidimensional array

Multidimensional array is an array of arrays. In layman's terms, it is to nest another array within the element value of an array variable. Multidimensional arrays can be divided into two-dimensional arrays, three-dimensional arrays, four-dimensional arrays, etc. To put it simply, a collection stores multiple collections, and each collection stores multiple elements.

In PHP language, use the array() function to create an array. The way to create a multi-dimensional array is to create another array at a certain element position of the original array. For example:

$students = array(
    array("John",21,"male"),
    array("Lily",23,"female"),
    array("Tom",20,"male"),
);

In the above code, $students is a two-dimensional array that contains three array elements. Each array element contains three string elements, representing the student's name, age, and gender respectively. .

2. The underlying implementation of PHP array

The array in PHP is a composite type, and its final implementation is to use a hash table, that is, a hash table. Hash tables are an important implementation of arrays that can support efficient insertion, search, and deletion operations.

When creating an array, PHP will allocate memory space for the array and store the key-value pair information of the array in the memory space. In PHP5, the array is actually a HashTable array handle composed of a zval structure, and the zval structure is a structure that saves various types of variable data in PHP.

3. The underlying implementation of multi-dimensional arrays

The underlying implementation of multi-dimensional arrays is similar to one-dimensional arrays, except that one dimension is added to the one-dimensional array. In PHP, a multidimensional array is essentially a hash table, but the value corresponding to each key is another hash table.

For example, for the following code:

$students = array(
    array("John",21,"male"),
    array("Lily",23,"female"),
    array("Tom",20,"male"),
);

The $students array can actually be viewed as containing three keys, and the value corresponding to each key is a three-element array. These three-element arrays are also implemented by hash tables.

The access method of multi-dimensional arrays is similar to that of one-dimensional arrays. You only need to access the corresponding keys step by step according to the number of layers. For example:

echo $students[1][0]; //输出Lily

In the above code, $students[1] accesses the second element and obtains a three-element array, and then accesses the first element of the array through [0], which results in the character Lily. string.

4. Application scenarios of multi-dimensional arrays

Multi-dimensional arrays are more suitable for storing and processing complex data structures due to their nested structures. In actual development, multidimensional arrays are often used in the following scenarios:

1. Table storage

Multidimensional arrays are often used to store table information, such as student information tables, product information tables, etc. By nesting arrays, you can easily store multiple records, each containing multiple fields.

2. Tree structure storage

Multidimensional arrays can also be used to store tree structure data, such as directory structures, comment replies, etc. By nesting arrays, the storage and traversal operations of tree structures can be realized, improving the flexibility and scalability of the program.

3. Complex data structure storage

The structure nesting characteristics of multi-dimensional arrays make it very suitable for storing complex data structures, such as graph structures, matrix structures, etc. By rationally constructing the structure of multi-dimensional arrays, the operation and processing of the corresponding data structure can be realized more efficiently.

5. Summary

This article focuses on the underlying implementation principles of PHP multi-dimensional arrays, and briefly introduces the application scenarios of multi-dimensional arrays. In fact, multi-dimensional arrays have wider application value and can be used in many programming fields. An in-depth understanding of the underlying implementation of multi-dimensional arrays is of very important guiding significance for PHP programmers. It can help us use multi-dimensional arrays more rationally and improve the efficiency and security of the program.

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