Summary of php array declaration, traversal, and array global variables

Php Tutorial: array declaration, traversal, array global variables

Copy codeThe 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 '<pre> ';
Print_r ($ user );
Echo '</pre> ';
// 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,
?>
Array super global variable
<? Php
/* Pre-defined array:
* Automatic global variable --- super Global Array
*
* 1. contains data from WEB servers, clients, runtime environments, and user input.
* 2. These arrays are special.
* 3. These arrays can be used directly if they take effect automatically within the global range.
* 4. Users cannot customize these arrays, but these arrays are operated in the same way as their own arrays.
* 5. You can directly use these arrays in functions.
*
* $ _ GET // variable submitted to the script through URL request
* $ _ POST // variables submitted to the script through the http post method
* $ _ REQUEST // variables submitted to the script through GET, POST, and COOKIE mechanisms
* $ _ FILES // variables submitted to the script by uploading FILES via the http post method
* $ _ COOKIE
* $ _ SESSION
* $ _ ENV // variables submitted to the script in the execution environment
* $ _ SERVER // The variable is set by the web server or directly associated with the execution environment of the current script.
* $ GLOBALS // as long as the variables are valid for the current script, the array key name is the name of the global script.
*
*
*/
// The Super global array can be directly called within the function.
$ Arr = array (10, 20); // a general array
$ _ GET = array (50, 90); // a super Global array
Function demo (){
Global $ arr; // You must include
Print_r ($ arr );
Print_r ($ _ GET); // you do not need to include a directly called Ultra-Global Array.
}

?>
<! -- *************************** -->
<? Php
// Directly use the passed value as a variable, which is useful when register_global = on is in the php. ini configuration file.
Echo $ username. "<br> ";
Echo $ email. "<br> ";
Echo $ page. "<br> ";
// The most stable value method
Echo $ _ GET ["username"]. "<br> ";
Echo $ _ GET ["email"]. "<br> ";
Echo $ _ GET ["page"]. "<br> ";
?>
<A href = "demo. php? Username = zhangsan & email = aaa@bbb.com & page = 45 "> this is a $ _ GET test </a>
<! -- ***************************** -->
<Form action = "demo. php" method = "post">
Username: <input type = "text" name = "uname"/> <br/>
Password: <input type = "password" name = "pass"/> <br/>
<Input type = "submit" value = "login"/> <br/>
</Form>
<? Php
Print_r ($ _ GET); // cannot receive
Print_r ($ _ POST); // to receive
?>
<? Php
// $ _ ENV usage
Echo '<pre> ';
Print_r ($ _ ENV );
Echo '</pre> ';
// Display the current environment
// You can also traverse
?>
<? Php
// Use the $ GLOBALS ultra-Global Array to call global variables within the Function
$ A = 100;
$ B = 200;
$ C = 300;
Function demo ()
{
// Directly call global variables
Echo $ GLOBALS ["a"]. "<br> ";
Echo $ GLOABLS ["B"]. "<br> ";
Echo $ GLOABLS ["c"]. "<br> ";

}
?>

Array Traversal
<? Php
/* Array Traversal
*
* 1. Use the for statement to traverse the array cyclically
* 1. Other languages (only in this way)
* 2. This method is not the preferred method in PHP.
* 3. The array must be an index array and the subscript must be continuous.
* (Index array subscripts can be discontinuous, and arrays can also be associated arrays. These two types cannot be traversed)
*
* 2. Use the foreach statement to traverse the array cyclically
* Foreacho (array variable as variable value ){
* // Loop body
*}
* 1. The number of loops is determined by the number of elements in the array.
* 2. Each loop assigns the elements in the array to the following variables respectively.
*
* Foreach (array variable as subscript variable => value variable ){
*}
*
*
* 3. while () list () each () combined loop traversal Array
*
* Each () function:
* 1. An array is required as a parameter.
* 2. The returned result is an array.
* 3. The returned array is 0, 1, key, and value subscripts (fixed)
* 0 and key subscript are the keys of the elements in the current parameter array.
* 1 and value subscript are the values of the elements in the current parameter array.
* 4. By default, the current element is the first element.
* 5. After each execution, the current element is moved backward.
* 6. If the last element executes this function, false is returned.
* List () function:
* 1. list () = array (); assign an array to this function.
* 2. The number of elements in the array must be the same as the number of parameters in the list () function.
* 3. Each element value in the array is assigned a value to each parameter in the list () function. list () converts each parameter to a variable.
* 4. list () can only accept indexed Arrays
* 5. assign values to parameters in the subscript order of indexes.
*
*
*
*/
// For statement to traverse the Array
$ User = array (1, "zhangsan", 40, "nan ");
For ($ I = 0; $ I <4; $ I ++)
{
Echo "$ user [{$ I}] =". $ user [$ I]. "<br> ";
}

// Use foreach
$ User = array (1, "zhangsan", 40, "nan ");
Foreach ($ user as $ val) // $ val is a custom variable
{
Echo $ val. "<br>"; // The output has nothing to do with the subscript.
}
Foreach ($ user as $ key => $ val) // $ val $ key is a custom variable
{
Echo $ key. "=====>". $ val. "<br> ";
}

// Foreach traverses multi-dimensional arrays
$ Info = array (
"User" => array (
// $ User [0]
Array (1, "zansan", 10, "nan "),
// $ User [1] [1]
Array (2, "lisi", 20, "nv"), // $ user [1]
// $ User [2]
Array (3, "wangwu", 30, "nan ")
),
"Score" => array (
Array (1,100, 90, 80 ),
Array (2, 99, 88, 11 ),
Array (3, 10, 50, 88)
),
"Connect" => array (
Array (1, '123', 'aaa @ bbb.com '),
Array (2, '123', 'bbb @ ccc.com '),
Array (3, '123', 'ccc @ ddd.com ')
)
);
Foreach ($ info as $ tableName => $ table)
{
Echo '<table align = "center" width = "500" border = "1"> ';
Echo '<caption> Foreach ($ table as $ row)
{
Echo '<tr> ';
Foreach ($ row as $ col)
{
Echo '<td>'. $ col. '</td> ';
}
Echo '</tr> ';
}
Echo '</table> ';
}

// Use of each ()
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
$ A = each ($ user); // Array ([1] => 1 [value] => 1 [0] => id [key] => id) the default value is the value of the first element.
Print_r ($ );
$ B = each ($ user );
Print_r ($ B); // Array ([1] => zhangsan [value] => zhangsan [0] => name [key] => name) each time, traverse one

$ C = each ($ user );
Print_r ($ c); // Array ([1] => 10 [value] => 10 [0] => age [key] => age)
$ D = each ($ user );
Print_r ($ d); // Array ([1] => nan [value] => nan [0] => sex [key] => sex)
$ E = each ($ user );
Var_dump ($ e); // bool (false) value returned when no element exists
// Each () and while Traversal
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
While ($ arr = each ($ user ))
{
// Echo $ arr [0]. "===> ". $ arr [1]. "<br>"; // displays the key (subscript) and value through 0, 1.
Echo $ arr ["key"]. "==>". $ arr ["value"]. "<br>"; // key and value are used to display key values.
}

// Use the list () function
List ($ name, $ age, $ sex) = array ("zhangsan", 10, "nnnnn ");
Echo $ name. "<br> ";
Echo $ age. "<br> ";
Echo $ sex. "<br> ";
// ANOTHER METHOD
List (, $ sex) = array ("zhangsan", 10, "nnnnn ");
Echo $ sex. "<br>"; // only convert gender to variable
// Ip judgment
$ Ip = "192.168.1.128 ";
List (, $ d) = explode (".", $ ip); // explode is separated by. And an array is returned.
Echo $ d; // retrieve 128
// List () can only receive indexed arrays.
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
List ($ key, $ value) = each ($ user); // Array ([1] => 1 [0] => id) assign values to the parameters in the list according to the order of the index, so the values are 0 and 1.
Echo $ key. "--->". $ value;
// While list () each () Combination
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
While (list ($ key, $ value) = each ($ user ))
{
Echo $ key. "--->". $ value. "<br> ";
}

// The solution is to display only once for multiple cycles
// Use the internal pointer control function of the array
// Next (array); move the array pointer to the next
// Prev (array); move the array pointer to the previous one
// Reset (array); move the array pointer to the first one (reset)
// End (array); the array pointer moves to the last one
// Current (array); obtains the value of the current element. The element pointed to by the index group pointer when the current element is present.
// Key (array); obtains the key value (subscript) of the current element)
$ User = array ("id" => 1, "name" => "zhangsan", "age" => 10, "sex" => "nan ");
While (list ($ key, $ value) = each ($ user ))
{
Echo $ key. "--->". $ value. "<br> ";
}
// Here, move the array pointer to the first loop below to output
// Reset ($ user)
While (list ($ key, $ value) = each ($ user) // The loop jumps out directly because each () returns false to the last one.
{
Echo $ key. "--->". $ value. "<br> ";
}
While (list ($ key, $ value) = each ($ user) // The loop jumps out directly because each () returns false to the last one.
{
Echo $ key. "--->". $ value. "<br> ";
}

Echo current ($ user). "====>". key ($ user );
?>