mysql_connect

说明

resource mysql_connect ( [string server [, string username [, string password [, bool new_link [, int client_flags]]]]] )

如果成功则返回一个 MySQL 连接标识，失败则返回 FALSE。

mysql_connect() 建立一个到 MySQL 服务器的连接。当没有提供可选参数时使用以下默认值：server = 'localhost:3306'，username = 服务器进程所有者的用户名，password = 空密码。

server 参数可以包括端口号。例如 "hostname:port" 或者是到本地套接字的路径，例如本机上的 ":/path/to/socket"。

注: 无论指定 "localhost" 或者 "localhost:port" 作为 server，MySQL 客户端库将覆盖之并尝试连接到本地套接字（Windows 中的名字管道）。如果希望使用 TCP/IP 连接，用 "127.0.0.1" 替代 "localhost"。如果 MySQL 客户端库试图连接到错误的本地套接字，则应该在 PHP 配置中将 mysql.default_host 设为正确的路径并使 server 字段为空。
":port" 的支持是 PHP 3.0B4 起加入的。
":/path/to/socket" 的支持是 PHP 3.0.10 起加入的。
可以在函数名前加上 @ 来抑制失败时产生的错误信息。

如果用同样的参数第二次调用 mysql_connect()，将不会建立新连接，而将返回已经打开的连接标识。参数 new_link 改变此行为并使 mysql_connect() 总是打开新的连接，甚至当 mysql_connect() 曾在前面被用同样的参数调用过。参数 client_flags 可以是以下常量的组合：MYSQL_CLIENT_COMPRESS，MYSQL_CLIENT_IGNORE_SPACE 或者 MYSQL_CLIENT_INTERACTIVE。

注: new_link 参数自 PHP 4.2.0 起可用。
client_flags 参数自 PHP 4.3.0 起可用。

一旦脚本结束，到服务器的连接就会被关闭。除非之前已经调用了 mysql_close() 来关闭它。

例子 1. MySQL 连接例子
<?php $link = mysql_connect("localhost", "mysql_user", "mysql_password") or die("Could not connect: " . mysql_error()); print ("Connected successfully"); mysql_close($link); ?>

参见 mysql_pconnect() 和 mysql_close()。

add a note User Contributed Notes

rui dot batista at netcabo dot pt
31-May-2006 11:42


Ever wonder what "default username" is?

<?php

$link = mysql_connect() or die(mysql_error());

$result = mysql_query("SELECT SESSION_USER(), CURRENT_USER();");

$row = mysql_fetch_row($result);

echo "SESSION USER: ", $row[0], "<br>\n";

echo "CURRENT USER: ", $row[1], "<br>\n";

?>

Both are ODBC@localhost in my win2k install, so my advice for windows is:

- create a MySQL user named ODBC with no password

- add localhost to ODBC user [right-click ODBC]

- set schema previleges to ODBC@localhost

- use mysql_connect() with no parms, or do not use ;)

This turns to work also with odbc_connect:

odbc_connect("myDSN", "", "")

Aesar
10-May-2006 01:26


That's an interesting discovery. I don't think it should be this way, but I think it's more a firefox/browser bug (at least, if you see it as a bug) than a fault in mysql/php.



What happens if you load the pages in two different browser screens instead of two tabs?

Mario
09-May-2006 12:21


PHP (5.1.2) stores connections according to script name and remote host, apparently. If the same script is requested by the same browser in two different tabs (Firefox for this test) and requests a non-persistent connection using the same user and password, the connection will be shared.



Ran into this while testing a script for concurrent usage using "LOCK TABLES" queries... and found that one tab's script was blocking until the other finished. No blocking occurred when different machines loaded the same script at the same time. Very interesting.

25-Jun-2005 06:18


connect to mysql via named pipe under windows :



in my.ini, add this:



[mysqld]

enable-named-pipe



then connect to the server, then connect to mysql using



mysql_connect('.')

camitz at NOSPAM dot example dot com
28-Oct-2004 04:05


A description about the problem with the password hashing and how to adress them can be found at http://dev.mysql.com/doc/mysql/en/Password_hashing.html

chaoscontrol_hq at yahoo dot com
24-Aug-2004 05:10


In MySQL4.1 and later, the default password hashing format has changed making it incompatible with 3.x clients.

I found out mysql_connect() works on server versions >= 4.1 when your MySQL user password is blank because password authentication isn't done in that case, otherwise you need to use another connection method (e.g. mysqli).

Also if you are using old MySQL tables on a new server (i.e. the passwords are stored in the old format), then the server will use the old auth method automatically and this function should work in all cases.

Hopefully this will help someone, it had me confused for a while because some of the users on my 4.1 server could connect and some couldn't.

martinnitram at excite dot com
31-Oct-2003 06:22


to use load data local infile function from mysql (at mysql 4.0.16, php 4.3.3), set fifth parameter of mysql_connect() to CLIENT_LOCAL_FILES(128), which based on MYSQL C API ( also mysql server support load file, check by "show variables like 'local_infile' ")



Thank  'phpweb at eden2 dot com' to point this out

phpweb at eden2 dot com
28-Jun-2003 02:55


client_flags can be things other than MYSQL_CLIENT_COMPRESS, MYSQL_CLIENT_IGNORE_SPACE and MYSQL_CLIENT_INTERACTIVE.



I presume that mysql_connect() just passes through to the C MySQL API, which provides these constants:



#define CLIENT_LONG_PASSWORD    1    /* new more secure passwords */

#define CLIENT_FOUND_ROWS    2    /* Found instead of affected rows */

#define CLIENT_LONG_FLAG    4    /* Get all column flags */

#define CLIENT_CONNECT_WITH_DB    8    /* One can specify db on connect */

#define CLIENT_NO_SCHEMA    16    /* Don't allow database.table.column */

#define CLIENT_COMPRESS        32    /* Can use compression protocol */

#define CLIENT_ODBC        64    /* Odbc client */

#define CLIENT_LOCAL_FILES    128    /* Can use LOAD DATA LOCAL */

#define CLIENT_IGNORE_SPACE    256    /* Ignore spaces before '(' */

#define CLIENT_CHANGE_USER    512    /* Support the mysql_change_user() */

#define CLIENT_INTERACTIVE    1024    /* This is an interactive client */

#define CLIENT_SSL              2048     /* Switch to SSL after handshake */

#define CLIENT_IGNORE_SIGPIPE   4096     /* IGNORE sigpipes */

#define CLIENT_TRANSACTIONS    8192    /* Client knows about transactions */



Not all of these may work or be meaningful, but CLIENT_FOUND_ROWS does, at least.

Graham_Rule at ed dot ac dot uk
14-May-2003 11:43


Another solution to the security problems of putting usernames and passwords into scripts. I haven't found this documented anywhere else so thought I'd suggest it for the online documentation. ........





Don't put passwords for mysql into scripts which may be read by any user on the machine.  Instead put them into an Apache configuration file and make sure that it is not world-readable. (Apache reads its main config files as root.)





For example, add this to your httpd.conf (and chmod it to 600 or 660) then tell your apache to reload itself (apachectl graceful).





<Directory /var/www/html/mydatabase>


    php_value mysql.default_user fred


    php_value mysql.default_password secret


    php_value mysql.default_host server.example.com


</Directory>





Then all you need in your PHP code is





$handle = mysql_connect() or die(mysql_error());





The passwords etc will only be picked up by scripts running in the named directory (or a sub-directory).  The same may be done for virtualhosts etc.





If you don't want to keep reloading your Apache server then you ay test things putting the php_value directives into a (world readable) .htaccess file. (Clearly not for production use.)





If you need to debug the values that are being supplied (or not) then use this snippet:





@syslog(LOG_DEBUG, "Using user=".ini_get("mysql.default_user").


            " pass=".ini_get("mysql.default_password").


            " host=".ini_get("mysql.default_host"));





(This assumes that you are not running in 'safe_mode' and that you are on a unix of some sort.)

amn -at- frognet.net
12-Mar-2003 02:40


Just in case you didn't know. You can use mysql_connect in a function to connect to a database and the connection is a super-global... meaning you can use mysql_query in other functions or in no function at all and PHP will use the connection that you opened. This is a handy bit of knowledge that helps if you have a large site with lots of scripts. If you create one function to connect to a db, and call that function in all your scripts, it makes for easier code maintenance since you only have to update one line of code to change your mysql connection instead of updating all your scripts individually.

rec0rder at lycos dot com
10-Apr-2002 02:54


The method I use to "protect" mySQL connect is to place dbConnect.php outside the web directory.



I will create a directory:

/var/include/



Put "dbConnect.php" into 

/var/include/



Edit your php.ini file to read "/var/include/" an include directory.



In your PHP now, you just have to do: 

require("dbConnect.php");

nospam at code24 dot com
27-Mar-2002 07:37


There should already be a post in here about this, but I would like to follow up on the idea that anyone can read your .inc files, which might contain username/password combos for mysql access.





There is a very simple way to block this.





If you are using Apache, just edit your httpd.conf file, and look for the following lines:





<Files ~ "^\.ht">


    Order allow,deny


    Deny from all


    Satisfy All


</Files>





Okay... that little chunk of text is saying that you don't want files that begin with .ht to be readable through apache. We also don't want people to see any files that end with .inc.





So, just add the following chunk of text to your httpd.conf file:





<Files ~ "\.inc(\.php)?$>


    Order allow,deny


    Deny from all


    Satisfy All


</Files>





This will block anyone from seeing your .inc files over the web.  It is much smarter than naming include files, "*.php".  Use the .php extension for your code, and save .inc for actual include data, and don't worry about people reading your .inc's anymore.





Hope this helps somebody.  Oh yeah... one other thing... obviously, anytime you make a change to httpd.conf (or whatever you have named your Apache config file), you must restart apache for the changes to take effect.

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