What is used to implement php arrays?

PHP is a server-side scripting language commonly used for web development. As a high-level programming language, PHP supports many data types, including integers, floating point numbers, strings, Boolean values, and objects. In PHP, array is a very commonly used data type used to store a set of related data. So, how are PHP arrays implemented?

In PHP, there are two types of arrays: indexed arrays and associative arrays. Indexed arrays store data according to numerical indexes, with each index associated with an element. Associative arrays store elements through specified keys, and each key is associated with a value.

The array implementation in PHP is a Hash table. A hash table is a common data structure that uses a hash function to map different keys to different locations, and quickly accesses and updates elements in an array by calculating the hash value of the key.

In PHP, the way an array is implemented is to store the hash value of the key and value in a hash table, and then when accessing the array element, PHP determines the hash value of the key by calculating the hash value of the key. position in and find the corresponding value at that position. If there are multiple keys with the same hash value, PHP will use a data structure such as a linked list or binary tree to handle them.

Technically speaking, the hash table in PHP is composed of buckets. Each bucket is a linked list or binary tree that stores key-value pairs with the same hash value. When the hash table needs to be expanded or shrunk, PHP will recalculate the hash value and reinsert all key-value pairs into the new bucket.

It is worth noting that the implementation of hash tables in PHP may vary between different versions. Prior to PHP 7.0, a hash table was actually an array of buckets, each bucket containing a pointer to a singly linked list. In PHP 7.0, the hash table is implemented by data slot (Datum slot), which improves the performance of the hash table.

In addition to hash tables, PHP also supports other types of data structures, such as balanced trees, skip tables, etc. However, hash tables are still the main way to implement arrays in PHP because they can complete insertion, deletion, and lookup operations in O(1) time complexity, and are easy to implement and debug.

In short, the implementation of PHP arrays is a hash table. Hash tables use hash functions to map different keys to different locations, and quickly access and update elements in the array by calculating the hash value of the keys. In PHP, a hash table usually consists of buckets, each bucket is used to store key-value pairs with the same hash value. This implementation method has the advantages of high efficiency, flexibility, easy implementation and debugging, making array operations in PHP more convenient and efficient.

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