Use the each() method to traverse the specified collection of elements. During traversal, the sequence number of the traversed elements is returned through the callback function. Its calling format is:
The parameter function is the callback function during traversal, and index is the sequence number of the traversed element, which starts from 0.
span class="green">peach grape lychee
----Use the remove() and empty() methods to delete elements
The
method deletes the selected element itself and its sub-elements. This method can specify certain elements that need to be deleted by adding filter parameters, while the
method only deletes the sub-elements of the selected element.
-> id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> username VARCHAR(20) NOT NULL,
-> password VARCHAR(32) NOT NULL,
-> age SMALLINT NOT NULL DEFAULT 10,
-> sex BOOLEAN
-> );
----Insert record INSERT
INSERT tbl_name [(col_name)] {VALUES|VALUE}...
If a field is omitted, all fields will be assigned values. If you want to keep the primary key incrementing at this time, just write the VALUE of the primary key as NULL/DEFAULT. Moreover, when fields are omitted, values must and can only be assigned to all fields. Each field must be assigned a value. If it does not match, an error will be reported
Note that there is more than one sorting standard here. The default ascending order is based on age. If the same ones are encountered, the same ones are sorted in descending order by id
----LIMIT limits the number of returns
mysql> SELECT * FROM users LIMIT 2,2; ---- ---------- ---------- ----- ---- -- | id | username | password | age | sex | ---- ---------- ---------- ----- -- ---- | 4 | Ben | 323 | 21 | 0 | | 5 | Ben | 323 | 10 | NULL | ---- ---------- - --------- ----- ------
It should be noted that if you write only one number 2, it means two numbers from the beginning; the 2,2 here means that two numbers will be returned from the third number, because the arrangement starts from 0 by default, so Here is the beginning of Article 3.
In addition, the order of restrictions has nothing to do with ID
mysql> SELECT * FROM users ORDER BY id DESC LIMIT 2; ---- ---------- ---------- ----- -- ---- | id | username | password | age | sex | ---- ---------- ---------- ----- ------ | 5 | Ben | 323 | 10 | NULL | | 4 | Ben | 323 | 21 | 0 | ---- --------- - ---------- ----- ------
----After learning SELECT
mysql> INSERT test(username) SELECT username FROM users WHERE age>=20;
mysql> SELECT * FROM test; ---- ---------- | id | username | ---- -------- -- | 1 | Tom | | 2 | Ben | ---- ----------
You can search and write in a targeted manner
----Summary
Record operation: add, update, delete and check
INSERT,UPDATE,DELETE,SELECT
3. Object-oriented
-----Basic Practice-----
----The concept of class
A class can be regarded as a "type of person", with the same "properties" and "methods" (but the corresponding values are not necessarily the same);
Attributes are inherent properties of the class
Methods are the "actions" of the class
The object of the class is called the instantiation of the class - the object is an individual belonging to the class, the concretization of the class
The attributes and methods of a class are class members
----Instantiation of class
Fill the class frame with specific data
/* * Code for object-oriented learning records */ //Definition class class nbaPlayer{ public $name=" Jordan"; public $height="198cm"; public $team="Bull";
public function __construct(){
}
public function run(){ echo "Runningn"; } } //Instantiation $jordan=new nbaPlayer(); //The calling object’s attributes and Method echo $jordan->name."n"; $jordan->run();
----Constructor
__construct
Default call, can be customized to give the default value of the class
The method of use is to write the variable in the function and give the value when instantiating it
/* * Code for object-oriented learning records */ //Definition class class nbaPlayer{ public $name; public $height; public $team;
public function __construct($name,$height,$team){ echo "constructingn";//determine whether the constructor is called $this->name=$name; //Use $this pseudo variable to pass parameters in the method $this->height=$height; $this->team=$team ; }
public function run(){ echo "Runningn"; } } //Instantiation $jordan=new nbaPlayer(" Jordan","198cm","Bull"); //Call the properties and methods of the object echo $jordan->name."n";
$jordan->run();
$james=new nbaPlayer("James", "197cm", "Heat");
Note that the constructor will be output twice here. In other words, the constructor is called once for each instantiation.
----Destructor
__destruct()
After writing the destructor,
function __destruct(){ echo "destructingn"; }
The results are as follows
constructing Jordan Running constructing destructing destructing
In other words, the destructor will be automatically called when the program ends
Alternatively, the destructor will also be called when the instantiated object is assigned a value of null
Generally used to clean up used resources
----Object reference
//Object reference $james1=$james;
$james2=&$james;
Among them, there is a reference of &, and the changes of the two objects are synchronized and can be regarded as a kind of image. Specifically, you can use the destructor mentioned above to simply verify.
http://www.bkjia.com/PHPjc/1067639.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1067639.htmlTechArticleWeb advanced jQuery operation DOM element MySQL record operation PHP object-oriented learning notes, web advanced jquerydom hi keep learning Quantity and Quality 1. jQuery operates DOM elements----use attr() method to control...
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
