Description:
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my comment on php.net (under egal at staerk dot de) is not 
reproducible under RedHat Linux, as RedHat's su is 
programmed not to accept passwords from a pipe. 
 
You can find out if the example will work with the command 
echo -e "password\n"|su 
where password is root's password 
If it rejects the password, the example will not work.