PHP Basic Tutorial

PHP Advanced Tutorial

PHP & MySQL

PHP Reference Manual

PHP CURL Functions PHP OpenSSL Functions

PHP mysqli_select_db() Function Usage and Example

The mysqli_select_db() function is used to change the default database for the connection.

Definition and Usage

mysqli_select_db()The function accepts a string representing the existing database and uses it as the default database.

Grammar

mysqli_select_db($con, name)

Parameter

Serial number	Parameters and descriptions
1	con(Required) This is an object representing the connection with the MySQL Server.
2	name(Required) This is a string value representing the database name.

Return value

The PHP mysqli_select_db() function returns a boolean value, which istrue,otherwisefalse.

PHP version

This function was originally in PHP version5introduced and can be used in all higher versions.

Online example

The following example demonstratesmysqli_select_db()Usage of the function (procedural style)-

Example

<?php
　　　//Establish connection
　　　$con = mysqli_connect("localhost", "root", "password", "mydb");
　　　//Select database
　　　mysqli_query($con, "CREATE DATABASE NewDatabase");
　　　mysqli_select_db($con, "NewDatabase");
　　　//Retrieve the current database name
　　　$res = mysqli_query($con, "SELECT DATABASE()");
　　　while ($row = mysqli_fetch_row($res)) {
　　　　　　print("Current database: ").$row[0];
　　　}
　　　//Close connection
　　　mysqli_close($con);
?>

Output result

Current database: newdatabase

Online example

In object-oriented style, the syntax of this function is$con-> select_db();.Here is an example of this function in object-oriented style;

Example

<?php
　　　//Establish connection
　　　$con = new mysqli("localhost", "root", "password", "mydb");
　　　//Retrieve the current database name
　　　$res = $con-> query("SELECT DATABASE()");
　　　while ($row = $res-> fetch_row()) {
　　　　　　print("Initial database: ").$row[0]."\n";
　　　}
　　　//Select database
　　　$con-> query("CREATE DATABASE NewDatabase");
　　　$con-> select_db("NewDatabase");
　　　//Retrieve the current database name
　　　$res = $con-> query("SELECT DATABASE()");
　　　while ($row = $res-> fetch_row()) {
　　　　　　print("Current database: ").$row[0];
　　　}
　　　//Close connection
　　　$res = $con　-> close();
?>

Output result

Initial database: mydb
Current database: newdatabase

Online example

In addition to specifying the database at the time of connection, you can also change the default connected database using this function later, as shown below:

Example

<?php
　　　//Establish connection
　　　$con = mysqli_connect("localhost", "root", "password");
　　　//Select database
　　　mysqli_select_db($con, "mydb");
　　　print("Select database ...\n");
　　　mysqli_query($con, "CREATE TABLE IF NOT EXISTS my_team(ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Place_Of_Birth VARCHAR(255), Country VARCHAR(255))");
　　　print("Create table ...\n");
　　　//Insert records into the my_team table
　　　mysqli_query($con, "insert into my_team values(")1, 'Shikhar', 'Dhawan', 'Delhi', 'India')");
　　　mysqli_query($con, "insert into my_team values(")2, 'Jonathan', 'Trott', 'Cape Town', 'South Africa')");
　　　mysqli_query($con, "insert into my_team values(")3, 'Kumara', 'Sangakkara', 'Matale', 'Sri Lanka')");
　　　mysqli_query($con, "insert into my_team values(")4, 'Virat', 'Kohli', 'Delhi', 'India')");
　　　print("Insert record ...\n");
　
　　　//Close connection
　　　mysqli_close($con);
?>

Output result

Select database ...
Create table ...
Insert record ...

Online example

Change the default database connection:

Example

<?php
　　　$connection_mysql = mysqli_connect("localhost", "root", "password", "mydb");
　　　
　　　if (mysqli_connect_errno($connection_mysql)){
　　　　　　echo "Failed to connect to MySQL: " . mysqli_connect_error();
　　　}
　　　
　　　$res = mysqli_select_db($connection_mysql, "testdb");
　　　
　　　if($res){
	　　　echo "Selected database";
　　　}else{
	　　　echo "An error occurred";
　　　}
　　　
　　　mysqli_close($connection_mysql);
?>

Output result

Selected database

PHP MySQLi Reference Manual

PHP CURL Functions PHP OpenSSL Functions