how to execute this command (sql command) in php? [duplicate]

I want to execute this query in php page.

the query:

BEGIN
SET @p=0;
UPDATE users SET cityrate = (@p:=@p+1) WHERE cityid=1 ORDER BY power DESC;
END

options (that dont work) that i already tried:

mysql_query(" BEGIN
SET @p=0;
UPDATE users SET cityrate = (@p:=@p+1) WHERE cityid=1 ORDER BY power DESC;
END");

and

mysql_query("SET @p=0;
UPDATE users SET cityrate = (@p:=@p+1) WHERE cityid=1 ORDER BY power DESC;");

Till now used this query on events but events aren't allowed on some hosts. so I am going to use this on cronjobs.

Pls help me.