sql injection

[sorpippo]

HI FOLKS.

How can I avoid the risk of sql injection in my scripts?

CIAO.

Giuseppe.

[linus]

What IS Sql injection?

[sorpippo]

HI FOLKS!

SQL injection is a big problem...
Suppose you have a query like this
SELECT user FROM users WHERE user='$u' AND passwd='$p'

if $u and $p come from a form and both contain
' OR ''='
the query above mentioned becomes
SELECT user FROM users WHERE user='' OR ''='' AND passwd='' OR ''=''

How php avoid this problem?

CIAO.

Giuseppe.