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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);
?>
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