Introduction
In this article I describe the PHP MySQLI functions mysqli_real_escape_string, mysqli_refresh, mysqli_rollback, mysqli_select_db and mysqli_set_charset. To learn some other MySQLI functions, go to:
- MySQLi Function in PHP: Part 1
- MySQLi Function in PHP: Part 2
- MySQLi Function in PHP: Part 3
- MySQLi Function in PHP: Part 4
- MySQLi Function in PHP: Part 5
- MySQLi Function in PHP: Part 6
- MySQLi Function in PHP: Part 7
- MySQLi Function in PHP: Part 8
- MySQLi Function in PHP: Part 9
- MySQLi Function in PHP: Part 10
PHP mysqli_real_escape() Function
The PHP MySQLi "mysqli_real_escape_string" function escapes special characters in a string for use in an SQL statement and this function returns an escaped string.
Syntax
| mysqli_real_escape_string(connection,escapeString); |
Parameters for the mysqli_real_escape function
The parameters of the function are:
| Parameter |
Description |
| string |
It specifies the MySQL connection to use. |
| escapeString |
It specifies the string to be escaped and characters encoded are nul( ASCII 0), \N,\r,\ and control z. |
Example
An example of the function is:
<?php
$con=mysqli_connect("localhost","root","","mysql");
if (mysqli_connect_errno($con))
{
echo "Unable to connect to MySQL: " . mysqli_connect_error();
}
$names="G'Gupta";
// This query will fail, cause we did not escape $newpers
mysqli_query($con,"INSERT into emp (name) VALUES ('$names')");
$newpers=mysqli_real_escape_string($con,$newpers);
// This query will work, cause we escaped $newpers
mysqli_query($con,"INSERT into emp (name) VALUES ('$names')");
mysqli_close($con);
?>
PHP mysqli_refresh() Function
The PHP MySQLi "mysqli_refresh" function refreshes tables or caches and this function returns true if the refresh was a success otherwise it returns false.
Syntax
| mysqli_refresh(connection,options); |
Parameters for the mysqli_refresh function
The parameters of the function are:
| Parameter |
Description |
| connection |
It specifies the mysql connection to use. |
| options |
It specifies the option to refresh and the options are:
- MYSQLI_REFRESH_GRANT: It refreshes the grant tables.
- MYSQLI_REFRESH_LOG: It flushes the logs.
- MYSQLI_REFRESH_TABLES: It flushes the table cache.
- MYSQLI_REFRESH_HOSTS: It flushes the host cache.
- MYSQLI_REFRESH_STATUS: It resets the status variables.
- MYSQLI_REFRESH_THREADS: It flushes the thread cache.
- MYSQLI_REFRESH_SLAVE: It resets the master server info, and restarts the slave.
- MYSQLI_REFRESH_MASTER: It removes the binary log files in the binary log index, and truncates the index file.
|
Example
An example of the function is:
<?php
$con=mysqli_connect("localhost","root","","mysql");
if (mysqli_connect_errno($con))
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
mysqli_refresh($con,MYSQLI_REFRESH_GRANT);
mysqli_close($con);
?>
PHP mysqli_rollbak() Function
The PHP MySQLi "mysqli_rollback" function rolls back the current transaction and this function returns true on success or false on failure..
Syntax
| mysqli_rollback(connection); |
Parameter for the mysqli_rollbak function
The parameter of the function is:
| Parameter |
Description |
| connection |
It specifies the MySQL connection to use. |
Example
An example of the function is:
<?php
$con=mysqli_connect("localhost","root","","mysql");
if (mysqli_connect_errno($con))
{
echo "Unable to connect: " . mysqli_connect_error();
}
// Set autocommit to off
mysqli_autocommit($con,FALSE);
// Insert some values
mysqli_query($con,"INSERT INTO emp(id,name,salary)VALUES (110,'Vikram',30)");<br>
//without commit it does not save the records
// Rollback transaction
mysqli_rollback($con);
mysqli_close($con);
?>
PHP mysqli_select_db() Function
The PHP MySQLi "mysqli_select_db" function selects the default database for database queries.
Syntax
| mysqli_select_db (connection, dbname); |
Parameters for the mysqli_select_db function
The parameters of the function are:
| Parameter |
Description |
| connection |
It specifies the MySQL connection to use. |
| dbname |
It specifies the default database to be used. |
Example
An example of the function is:
<?php
$con=mysqli_connect("localhost","root","","mysql");
if (mysqli_connect_errno($con))
{
echo "Unable to connect: " . mysqli_connect_error();
}
//write PHP code foe "mysql" database
mysqli_select_db($con,"test");
// write PHP code foe "test" database
mysqli_close($con);
?>
PHP mysqli_set_charset() Function
The PHP MySQLi "mysqli_real_escape_string" function sets the default client character set and this function returns true on success or false on failure.
Syntax
| mysqli_set_charset(connection,charset); |
Example
An example of the function is:
<?php
$con=mysqli_connect("localhost","root","","mysql");
if (mysqli_connect_errno($con))
{
echo "Unable to connect: " . mysqli_connect_error();
}
mysqli_set_charset($con,"utf8");
mysqli_close($con);
?>