Table of Contents for

MySQL in a Nutshell, 2nd Edition

Use this function to start a MySQL connection. The first argument of the function is the server name. If none is specified, localhost is assumed. A port may be specified with the server name (separated by a colon) or a socket along with its path. If no port is given, port 3306 is assumed. The username is to be given as the second argument and the user’s password as the third. If a connection is attempted that uses the same parameters as a previous one, the existing connection will be used and a new connection link will not be created unless new_link is specified as the fourth argument of this function. As an optional fifth argument, client flags may be given for the MySQL constants MYSQL_CLIENT_COMPRESS, MYSQL_CLIENT_IGNORE_SPACE, MYSQL_CLIENT_INTERACTIVE, and MYSQL_CLIENT_SSL. The function returns a connection identifier if successful; it returns false if it’s unsuccessful. Use mysql_close() to close a connection created by mysql_connect(). Here is an example:

#!/usr/bin/php -q
<?
   mysql_connect('localhost', 'ricky', 'adams');
   mysql_select_db('workrequests');
...

To be able to identify the connection link later, especially when a script will be using more than one link, capture the results of mysql_connect(). Here is a complete script that sets up two connections to MySQL and captures the resource identification number for each link:

#!/usr/bin/php -q
<?
$user1 = 'elvis';
$user2 = 'fats';
$connection1 = mysql_connect('localhost', $user1, 'ganslmeier123');
$connection2 = mysql_connect('localhost', $user2, 'holzolling456');
mysql_select_db('workrequests', $connection1);
mysql_select_db('workrequests', $connection2);
counter($connection1,$user1);
counter($connection2,$user2);
function counter($connection,$user) {
   $sql_stmnt = "SELECT * FROM workreq";
   $results = mysql_query($sql_stmnt, $connection);
   if(mysql_errno($connection)){
      print "Could not SELECT with $connection for $user. \n";
      return;
   }
   $count = mysql_num_rows($results);
   print "Number of Rows Found with $connection for $user:
          $count. \n";
}
mysql_close($connection1);
mysql_close($connection2);
?>

In this example, two links are established with different usernames. The counter() subroutine is called twice, once with each connection identifier and username passed to the user-defined function. For the first connection, the user elvis does not have SELECT privileges, so the SQL statement is unsuccessful. An error is generated and the number of rows is not determined due to the return ending the function call. For the second connection, the user fats has the necessary privileges, so the function is completed successfully. Here is the output from running this script on my server:

Could not SELECT with Resource id #1 for elvis.
Number of Rows Found with Resource id #2 for fats:  528.