This shouldn't be an issue. The data should not be stored with escaping backslashes.
You have one of two problems:
1) This is least common.. Make sure magic_quotes_runtime is off in the PHP ini. You can also turn this off using set_magic_quotes_runtime(0) in your scripts.
2) The most common reason for this is that magic_quotes_gpc is on AND you are using addslashes() before inserting into the database. magic_quotes_gpc is a GOOD thing when you commonly use form element values in db queries as it saves you from having to manually addslashes(). If magic_quotes_gpc is on, don't use addslashes(). When you use both you'll end up double escaping the data resulting in an escaped entry in the db which causes your problem.
IOW, let's say someone enters
o'brien
in your form. With magic_quotes_gpc on, when the form is submitted, PHP will automatically add the slash to escape the single quote and
o'brien
will become
o\'brien
which is ready for db insert and will store correctly as
o'brien
But if you also use addslashes()
o'brien
will be
o\'brien
after submittal, then addslashes changes it to
o\\'brien
resulting in
o\'brien
being stored in the database.
HTH
