MySQL Database Connection


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Opening Database Connection

PHP provides mysql_connect function to open a database connection. This function takes five parameters and returns a MySQL link identifier on success, or FALSE on failure.

Syntax

connection mysql_connect(server,user,passwd,new_link,client_flag);
Parameter Description
serverOptional - The host name running database server. If not specified then default value is localhost:3306.
userOptional - The username accessing the database. If not specified then default is the name of the user that owns the server process.
passwdOptional - The password of the user accessing the database. If not specified then default is an empty password.
new_linkOptional - If a second call is made to mysql_connect() with the same arguments, no new connection will be established; instead, the identifier of the already opened connection will be returned.
client_flagsOptional - A combination of the following constants:
  • MYSQL_CLIENT_SSL - Use SSL encryption
  • MYSQL_CLIENT_COMPRESS - Use compression protocol
  • MYSQL_CLIENT_IGNORE_SPACE - Allow space after function names
  • MYSQL_CLIENT_INTERACTIVE - Allow interactive timeout seconds of inactivity before closing the connection

NOTE: You can specify server, user, passwd in php.ini file instead of using them again and again in your every PHP scripts. Check php.ini file configuration.

Closing Database Connection

Its simplest function mysql_close PHP provides to close a database connection. This function takes connection resource returned by mysql_connect function. It returns TRUE on success or FALSE on failure.

Syntax

bool mysql_close ( resource $link_identifier );

If a resource is not specified then last opend database is closed.

Example

Try out following example to open and close a database connection:

<?php
$dbhost = 'localhost:3036';
$dbuser = 'guest';
$dbpass = 'guest123';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
  die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully';
mysql_close($conn);
?>

php_and_mysql.htm