You can't use PHP variables *DIRECTLY*, but you can pass them in as parameters.
For example, using the getAndBumpCount SP that I created, you would invoke it from PHP via:
$sql = "call getAndBumpCount ('$name')";
$result = mysql_query( $sql );
You can pass in as many arguments as you wish to a Stored Procedure and then use them by name in the body of the procedure.
In my SP, I used
create procedure getAndBumpCount( nm varchar(20) )
so the argument $name would end up in the MySQL variable nm
and you can then use nm
wherever you want in the SP.
Some people use a naming convention for parameters. Such as P_NM, P_ID, P_Address, etc. Where the "P_" makes it clear that this variable is a "P"arameter to the stored procedure.