Array declaration for php learning

Php learning array declaration implementation code. For more information, see. The code is as follows:

/*
* 1. Array Overview
* 1. the essence of arrays: managing and operating a group of variables, batch processing
* 2. array composite type (multiple objects can be stored)
* 3. data of any length or type can be stored in an array
* 4. arrays can be used to complete data structures in other languages (linked lists, queues, stacks, and collection classes)
*
*
*
* 2. array classification
* The array contains multiple units (elements)
* Each element (subscript [key] and value)
* When accessing a single element, all elements are accessed by subscript (key ).
* 1. one-dimensional array, two-dimensional array, and three-dimensional array... Multi-dimensional array
* (The array contains other arrays)
* 2. PHP has two types of arrays.
* Index array: index where the subscript is an ordered integer
* Associated array: the subscript is a string as an index.
*
* Only these two subscripts (integers and strings) exist.
*
*
* 3. multiple array declaration methods
*
* 1. directly assign a value to an array element
* If the index subscript is not given, the index starts from 0.
* If an index subscript is given, the next index increases by 1 from the maximum.
* If the subscript appears next to it, if it is a value assignment, it is to re-assign the value to the previous element.
* When a hybrid declaration is made, the index and association do not affect each other (the Declaration of the index subject is not affected)
*
* 2. use the array () function declaration
* The default value is an index array.
* If you specify a subscript for the associated array and index array, use the key => value
* Use "," to separate multiple members
* 3. use other function declarations
*
*
*
*
*/
// Index the array
$ User [0] = 1; // user serial number
$ User [1] = "zhangsan"; // user name
$ User [2] = 10; // age
$ User [3] = "nan"; // gender
Echo'

'; 
print_r($user); 
echo '

';
// Associate an array
$ User ["id"] = 1;
$ User ["name"] = "zhangsan ";
$ User ["age"] = 10;
$ User ["sex"];
$ User ["age"] = 90; // value assignment
Echo $ user ["name"]; // output
// Use array () to declare an array
$ User = array (1, "zhangsan", 10, "nan ");
// Declare the joined array using array ()
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
// Declare multi-dimensional arrays (multiple records) to save multiple user information records in a table
$ User = array (
// Call this line with $ user [0]. for example, call the name in this record, $ user [0] [1]
Array (1, "zhangsan", 10, "nan "),
// Call this line with $ user [1]. for example, call the name in this record, $ user [1] [1]
Array (2, "lisi", 20, "nv ")
);
// Multiple tables are saved in an array. Each table has multiple records.
$ Info = array (
"User" => array (
Array (1, "zhangsan", 10, "nan "),
Array (2, "lisi", 20, "nv ")
),
"Score" => array (
Array ),
Array (2, 60, 40, 70)
)
);
Echo $ info ["score"] [1] [1]; // output 60,
?>