Summary of PHP array declaration, traversal, and array global variable usage

PHP tutorial: array declaration, traversal, array global variables

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/*
* 1. Overview of arrays
* 1. The essence of arrays: manage and operate a set of variables, batch processing
* 2. Arrays Composite type (can store multiple)
* 3. Arrays can store data of any length and any type of data
* 4. Arrays can complete the functions of other language data structures (linked lists, queues , stack, collection class)
*
*
*
* 2. Classification of arrays
* There are multiple units in the array, (units are called elements)
* Each Element (subscript [key] and 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)
* 2. There are two types of arrays in PHP
* Index array: It is an index whose subscript is a sequential integer
* Associative array: The subscript is a string as an index
*
* There are only two types of subscripts (integer, string)
*
*
* 3. Multiple arrays Declaration method
*
* 1. Directly assign a value to the array element declaration
* If the index subscript is not given, the sequential index will start from 0
* If the index subscript is given, the next It will increase by 1 starting from the largest
* If the previous subscript appears later, if it is an assignment, the previous element will be reassigned
* When mixed declaration, index and association do not affect each other (it does not affect the index subscript) Declaration)
*
* 2. Use the array() function to declare
* The default is an index array
* If you specify a subscript for an associative array and an index array, use key => value
* Use " , " to split
* between multiple members. 3. Use other function declarations
*
*
*
*
*/
//Index array
$user[0]=1;//User serial number
$user[1]="zhangsan";//User name
$user[2]=10;//Age
$ user[3]="nan";//Gender
echo '

'; <br>print_r($user); <br>echo '

';
//Association Array
$user["id"]=1;
$user["name"]="zhangsan";
$user["age"]=10;
$user["sex "];
$user["age"]=90;//Assignment
echo $user["name"];//Output
//Use array() to declare the array
$user =array(1,"zhangsan",10,"nan");
//Use array() to declare an associative array
$user=array("id"=>1,"name"=> "zhangsan","age"=>10,"sex"=>"nan");
//Declare a multi-dimensional array (multiple records) to save multiple user information records in a table
$user=array(
//Use $user[0] to call this line, such as calling the name in this record, $user[0][1]
array(1,"zhangsan",10 ,"nan"),
//Use $user[1] to call this line, such as calling the name in this record, $user[1][1]
array(2,"lisi",20 ,"nv")
);
//Array saves multiple tables, each table has multiple records
$info=array(
"user"=>array(
array(1,"zhangsan",10,"nan"),
array(2,"lisi",20,"nv")
),
"score"=>array(
array(1,90,80,70),
array(2,60,40,70)
)

);
echo $info["score"][1 ][1];//Output 60,
?>
Array super global variable
/* Predefined array:
* Automatic global variable---super Global array
*
* 1. Contains data from the WEB server, client, operating environment and user input
* 2. These arrays are special
* 3. Automatically take effect in the global scope, These arrays can be used directly
* 4. Users cannot customize these arrays, but the operations of these arrays are the same as those defined by themselves
* 5. These arrays can be used directly in functions
*
* $_GET //Variables submitted to the script via URL request
* $_POST //Variables submitted to the script via HTTP POST method
* $_REQUEST //Via GET, POST and COOKIE mechanisms Variables submitted to the script
* $_FILES //Variables submitted to the script via http post method file upload
* $_COOKIE
* $_SESSION
* $_ENV //Execution environment submitted to the script Variables
* $_SERVER //Variables are set by the WEB server, or directly associated with the execution environment of the current script
* $GLOBALS //As long as the variables that are valid for the current script are here, the keys of the array The name of the global script
*
*
*/
//Super global array can be called directly inside the function
$arr=array(10,20);//General array
$_GET=array(50,90);//Super global array
function demo(){
global $arr;//When calling global variables, you must first include
print_r($arr);
print_r($_GET);//Directly call the super global array without including
}

?>

//Use the passed value directly as a variable. Useful when register_global=on in the php.ini configuration file.
echo $username."
";
echo $email."
";
echo $page."
";
//The most stable Value method
echo $_GET["username"]."
";
echo $_GET["email"]."
";
echo $_GET["page "]."
";
?>
this is a $_GET test< /a>

username:

password:< ;input type="password" name="pass" />

< ;/form>
print_r($_GET);//Cannot receive
print_r($_POST);//This is how to receive
?>
< ;?php
//Usage of $_ENV
echo'