Front-end PHP entry -033-Connect database-Tianlong eight steps

Does PHP check for MySQL support turned on?

If you do not see the mysqli extension under Windows Server, open the php.ini file, open the Php_mysqli.dll!

注意：

MySQL extensions are no longer supported by default from PHP7, that is, mysql_* series functions are no longer supported. Please use mysqli to connect to the database.

MYSQLI support PHP5 also supports PHP7.

Database Connection Tianlong Eight step one step: Connect to the database server

type	Description
Function	Mysqli_connect
Function	Connecting to a MySQL database server
Parameter 1	Host
Parameter 2	Database Server login Name
Parameter 3	Password
Parameter 4	Name of the database
Parameter 5	Database server port does not fill default 3306

If parameter 4, the database name is filled and selected in this step, no third step is required.

Step Two: Judging errors

type	Description
Function	Mysqli_errno
Function	Return connection error number, no error returned 0
Parameter 1	Resources returned by incoming Mysqli_connect

type	Description
Function	Mysqli_error
Function	Returns the connection error string
Parameter 1	Resources returned by incoming Mysqli_connect

Step three: Select a database

type	Description
Function	mysqli_select_db
Function	Select a database in this connection
Parameter 1	Resources returned by incoming Mysqli_connect
Parameter 2	The name of the database that needs to be connected

If you have completed the first step of the database, you do not need to change to another database, you do not need to perform a third step.

Fourth step: Setting the character set

type	Description
Function	Mysqli_set_charset
Function	Set the connection with MySQL power, result, check character set
Parameter 1	Resources returned by incoming Mysqli_connect
Parameter 2	Character set type

Fifth step: Preparing SQL statements

is actually a string of SQL statements.

For example:

sq L="INseRTINTouseR(useRName,PassWoRd )vaLues (the s q l = " i n s e R t i n t o u s e R ( u s e R N a m e , p A s s w o r d ) v a l u e s ( the Username ', ' $password ') ";

We usually use variables in SQL statements to assign values. However, the variable or SQL statement error, very difficult to troubleshoot.

We have added this step in the light of actual work experience.

If you make an error while performing this step, we can print out the SQL statement and paste it into the phpMyAdmin or related tool.

If the execution succeeds, it is not an issue with the SQL statement. If execution fails, double-check the SQL statement.

Sixth step: Send SQL statements

type	Description
Function	Mysqli_query
Function	Send SQL statement
Parameter 1	Resources returned by incoming Mysqli_connect
Parameter 2	Incoming sent SQL statement

The SQL statement is ready to be completed and the SQL statement needs to be sent to the MySQL server via Mysqli_query.

The MySQL server executes the SQL statement sent over.

Seventh step: Determine whether to perform normal or traverse data read

In the 6th step, the statements for the Select category are sent, and the result output is usually displayed. You need to use a function that iterates through the display data.

type	Description
Function	Mysqli_fetch_array
Function	Gets the data in the result set, returns the array to traverse
Parameter 1	Result variables passed in the query
Parameter 2	Incoming Mysqli_num returns an indexed array, MYSQLI_ASSOC returns an associative array, Mysqli_both returns an index and an association

type	Description
Function	Mysqli_fetch_assoc
Function	Get data in result set, return associative array for convenience
Parameter 1	Result variables passed in the query

type	Description
Function	Mysqli_fetch_row
Function	Get data in result set, return index array for convenience
Parameter 1	Result variables passed in the query

type	Description
Function	Mysqli_fetch_object
Function	Get data in result set, return object for traversal
Parameter 1	Result variables passed in the query

type	Description
Function	Mysqli_num_rows
Function	Returns the total number of results from the query
Parameter 1	Result variables passed in the query

type	Description
Function	Mysqli_num_rows
Function	Returns the total number of results from the query
Parameter 1	Result variables passed in the query
Note	Use very little in the actual work, understand

Write

In the 6th step, if you send an INSERT statement, you usually need to get the success of the execution, or get the self-increment ID at the same time.

type	Description
Function	Mysqli_fetch_field
Function	Traversing data rows
Parameter 1	Result variables passed in the query

Modify and delete

In the 6th step, if you are sending statements for the update and delete categories. You only need to determine if the execution succeeds.

We'll show you the data sheets for these common functions.

Eighth step: Close the database

type	Description
Function	Mysqli_close
Function	To close a database connection
Parameter 1	Resources returned by incoming Mysqli_connect

A database connection is a resource type. We told you about the resource types in the previous chapters. Any type of resource that involves a number of resources is opened and closed. This ensures that PHP can process and recycle resources more efficiently.

Therefore, when the database connection succeeds, it does not need to be used. We can close this connection.

Other: Display server information functions

type	Description
Function	Mysqli_get_server_info
Function	Return server information
Parameter 1	Resources returned by incoming Mysqli_connect

type	Description
Function	Mysqli_get_server_version
Function	Back to server version
Parameter 1	Resources returned by incoming Mysqli_connect

Note: The connection of PDO is the kingly way
Mysqli only learn the process of the method can be. In the object-oriented phase, the object usage of mysqli is completely discarded, but the way that the PDO objects connect to the database is used.

From for notes (Wiz)

Front-end PHP entry -033-Connect database-Tianlong eight steps