sort array by index

In actual development, more or less will encounter array sorting problem, in addition to the conventional write simple sorting algorithm, PHP also provides a built-in array sorting function, this time to share the key: Uasort   Use user-defined

1. The concept of arrays An array is a named range that is used to store a series of variable values. Each array element has an associated index (also a keyword) that can be used to access elements. PHP allows you to use numbers or strings evenly

Basic functions of array manipulationThe key name and value of the arrayArray_values ($arr); Get the value of an arrayArray_keys ($arr); Gets the key name of the arrayArray_flip ($arr); the values in the array are exchanged with the key names (if

basic functions of array manipulationThe key name and value of the arrayArray_values ($arr); Gets the value of the array Array_keys ($arr), gets the key name of the array array_flip ($arr), and the values in the array are exchanged with the key

Sequence (two)The sorting algorithm above has one property: in the last result of sorting, the order of each element depends on the comparison between them . We call this sort of sorting algorithm a comparative sort .Whatever the lower bound of the

PHP has a lot of functions about arrays to facilitate array manipulation. Defined: Each entity of an array contains two items: key and value, which can be retrieved by a query key. These keys can be numeric (numerical) or associated (associative)

One, index type (a), one -touch index The index created on one key is the one-touch index, and the single key index is the most common index, such as the _id index created by default by MongoDB. (ii), composite index Indexes built on multiple keys

First, the index introductionIn MongoDB, indexes are used to support efficient queries. If there is no index, MONGODB must scan each document in the entire collection to find a matching document. However, if an appropriate index is established,

_ Id Index An index is automatically created for the _ id field for all sets except the set of capacity. This is a special index and cannot be deleted. The _ id index forces that its keywords are unique (except for some scenarios in the partition

Learn PHP's array summary "experience", PHP array Summary PHP has a lot of functions for arrays, which makes it easy to manipulate arrays. Defined: The array contains two items per entity: Key and value, which can be obtained by querying the key.