The difference between php array and linked list

The difference between arrays and linked lists in PHP

From the perspective of logical structure

1. , the array must have a fixed length (number of elements) defined in advance, and cannot adapt to the dynamic increase or decrease of data. When the data increases, the number of elements may exceed the originally defined number; when the data decreases, memory waste occurs; the array can be directly accessed according to the subscript.

2. The linked list dynamically allocates storage, which can adapt to the dynamic increase and decrease of data, and can easily insert and delete data items. (When inserting or deleting data items in the array, other data items need to be moved, which is very cumbersome.) The linked list must find the next element based on the next pointer.

From the perspective of memory storage

1. (static) arrays allocate space from the stack, which is convenient and fast for programmers, but the degree of freedom is small.

2. The linked list allocates space from the heap, which has a large degree of freedom but is more troublesome to apply for and manage.

It can be seen from the above comparison that if you need to access data quickly and rarely or without inserting and deleting elements, you should use an array; on the contrary, if you need to frequently insert and delete elements, you need to use a linked list data structure. .

Supplement:

Arrays store elements continuously in memory. Since each element occupies the same memory, any element in the array can be quickly accessed through subscripts. But if you want to add an element to the array, you need to move a large number of elements, free up space for one element in the memory, and then place the element to be added there.

Similarly, if you want to delete an element, you also need to move a large number of elements to fill in the moved elements. If your application requires fast access to data, with few or no insertions and deletions of elements, you should use arrays.

The linked list is just the opposite. The elements in the linked list are not stored sequentially in the memory, but are linked together through pointers that exist in the elements. For example: the previous element has a pointer pointing to the next element, and so on, until the last element.

If you want to access an element in the linked list, you need to start from the first element and find the required element position. But adding and deleting an element is very simple for the linked list data structure. Just modify the pointer in the element. If your application requires frequent insertion and deletion of elements you will need to use a linked list data structure.

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