How to store php array

PHP is a widely used programming language, especially in the development of web applications. In PHP, array is a very commonly used data type, used to store a group of similar data. So, how are PHP arrays stored? Let’s take a closer look below.

In PHP, arrays can be divided into two types: indexed arrays and associative arrays. An index array stores a set of data in order and is automatically assigned a numeric key, while an associative array uses a custom storage method where keys and values ​​correspond one to one. No matter what type of array they are, their underlying implementation is implemented through a hash table.

Hash table is a data structure that stores data based on key-value pairs. It achieves fast processing by converting the key into a hash value and then mapping the hash value to a position in the array. data access. In PHP, the underlying hash table implementation is a dynamic array based on hash tables. When an array is created, it allocates a dynamically allocated memory area that grows dynamically with the size of the array.

When we add an element to an array, PHP will first check whether there is already a corresponding key value in the array. If so, it will directly replace the old value with the new value; if not, it will Find the corresponding subscript to store data based on the hash value of the key. If the hash values ​​collide (i.e. multiple keys have the same hash value), PHP uses a linked list to concatenate these key-value pairs together and store them in the same bucket. When we need to access an array element, PHP will first calculate the hash value of the element, and then find the location of the element in the corresponding bucket based on the hash value.

In addition to hash tables, PHP also has some other data structures for storing arrays. For example, in some cases, PHP uses ordered arrays to store index arrays. In this case, the keys of the array are sequential integers, and the keys correspond to the values ​​one-to-one. Using sequential arrays during storage can improve access efficiency. For some sparse associative arrays, a combination of dense array (Dense Array) and sparse array (Sparse Array) will be used to store only elements with values.

To sum up, the storage method of PHP array is based on the hash table of hash table. PHP will dynamically allocate a memory area to store the array. At the same time, different selections will be made according to the type and number of elements of the array. storage structure to improve access efficiency and reduce memory usage. For PHP developers, these underlying details do not need to be understood in depth. We only need to master the basic operations of arrays, so that we can flexibly use arrays to store data in development.

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