Overview and classification and declaration code demonstration of php array_PHP tutorial

/**
** Overview of an array
1. The essence of an array: manage and operate a set of variables, batch processing
2. Arrays are composite types
3. Arrays can store data of any length . It can also store any type of data
4. Arrays can complete the functions of other language data structures (linked lists, queues, stacks, collection classes)
**
2. Classification of arrays
In arrays There are multiple units, (units are called elements)
Each element is composed of a subscript [key] and a value
When accessing an element individually, the element is accessed through the subscript [key]
1. One-dimensional array, two-dimensional array, three-dimensional array. . . . . Multidimensional array
(an array of arrays means that other arrays are stored in the array)

There are two kinds of arrays in 2.php
index array: the subscript [key] is a sequential integer Index
associative array: subscript is string as index
subscript (integer, string) There are only two
*
three. Multiple declaration methods for arrays
1 Directly assign values ​​to array elements
If the index subscript is not given, the sequential index will start from 0
If the index subscript is given, the next one will be increased from the largest 1
If the previous subscript appears later, if it is an assignment, the previous element will be reassigned
d When the mixed declaration is made, the index and association do not affect each other (it does not affect the declaration of the index subscript)
2 Use array () Function

a defaults to index array
b. If you specify subscripts for associative arrays and index arrays, use key => value
c Use "," to separate multiple members;
3 Use other function declarations
file();

*
*
*
*
**/

echo $arr[5]

//Index array
$user[]=1;
$user[9]="Zhang San"
$user[0]=10;
$user[3]="nan";
$info=array(
"$user"=array(
//$user[0]
array("1", "Zhang San",10,"nan"),
//$user[1]
array("2","lisi",10,"nan"),
//$user[ 2]
array("3","wangwu",10,"nan"),
),
"$score"=array(
//$user[0]
array("1","张三",10,"nan"),
//$user[1]
array("2","lisi",10,"nan"),
//$user[2]
array("3","wangwu",10,"nan"),
),

"$connect"=array(
/ /$user[0]
array("1","Zhang San",10,"nan"),
//$user[1]
array("2","lisi", 10,"nan"),
//$user[2]
array("3","wangwu",10,"nan"),
),
};

$user[][]=1;
$user[][]=1;
$user[][]=1;
$user[][]=1;
$user[][]=1;

?>