How can i do record level locking using PHP?

[Munish Aggarwal]

version that i am using
PHP version=4.3.1
Mysql version=4.0.22-nt

I have problem in taking the record level locking.
When i take the lock on MYSQL command line . it works

mysql>begin work;
mysql>select * from tblemp where empid=1 for update;

Now no other user is able to update the record of empid=1.
untill i run the command

mysql>commit;

but when i tried this thing by PHP code. it does not work.

One more thing, how can i use the same link that i have created on other php page.I do not want to creat link again and again for every new php page by code

$link = mysql_connect($Server,$Usr,$Pwd);

i want $link as global and can be user directly on any page if once is created.
i have also tried by making the $link to global variable. but not working
Help me out from these problems