What is index array in php

Index array in php is a basic array type. Each element of it has a numeric index, which is automatically assigned and numbered continuously, starting from 0 and increasing in sequence. Its syntax format is: $arrayName = array(value1, value2, value3…).

Operating system for this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

What is an indexed array

In PHP, an array is a data structure used to store values, the elements of which are accessed through indexes. But there are two different types of arrays in PHP: associative arrays and indexed arrays. Among them, the index array is a basic array type. Each element of it has a numeric index, which is automatically assigned and numbered continuously, starting from 0 and increasing in sequence. Its syntax format is: $arrayName = array(value1, value2, value3…).

$cars = array("Volvo", "BMW", "Toyota");

The above example introduces how to use the index array, which consists of three string elements with index values ​​0, 1 and 2 respectively. We can iterate through the index array as follows.

Advantages of using indexed arrays

Indexed arrays are frequently used in ordinary programming, and they provide several advantages.

Using indexed arrays is very convenient when storing sequentially, because we do not need to specify the key explicitly, and the system automatically assigns the index of each element. Looping with an indexed array is faster because an index value can be converted into a memory address, making the array accessible in constant time. Indexed arrays leverage the general definition of an array, which is a natural representation of an ordered collection of values. In PHP, indexed arrays are similar to many other programming languages, making it easier to learn PHP programming.

How to use index array

When we create an index array, both methods are available.

Use the "array" keyword, which is an alias of the "array()" function. Use "[]" syntax.

The following are some examples of creating indexed arrays:

//使用“array”关键字。
$cars = array("Volvo", "BMW", "Toyota");
//使用“[]”语法。
$cities = ["New York", "London", "Paris"];

When we want to access an array element, we can use a subscript to access it.

echo $cars[0];         //输出"Volvo"
echo $cities[2];       //输出"Paris"

Best Practices

Indexed arrays are one of the most common array types in PHP. When we use it, there are some best practices that are worthy of our attention. of.

To improve readability and ease of maintenance, store only one value in each row of the array whenever possible. Whenever possible, use actual numeric indexes rather than strings to represent indexes, which can reduce the amount of memory stored. When arrays get larger, avoid using quicksort functions; using these functions to sort on large collections may cause performance issues.

For example:

//正确的写法
$cars = array("Volvo", "BMW", "Toyota");
$car1 = $cars[0];
$car2 = $cars[1];
$car3 = $cars[2];
//错误的写法
$cars = array("Volvo", "BMW", "Toyota", "Volkswagen", "Audi", "Mercedes", 
                    "Honda", "Jeep", "Lexus", "Mazda", "Nissan", "Acura", "Mitsubishi");
sort($cars);

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