problem with apostrophe

I am using mysql with PHP. I have a problem with inserting the apostrophe value in database. However I use -

$newstring = str_replace("'","'",$string);

OR

$newstring = str_replace("'","''",$string);

but how could I fetch the string as it is?

Thanks.

Use mysql_real_escape_string:

mysql_real_escape_string($string)

you need to escape it, use addslashes() to sanitise it, or better yet, mysql_real_escape_string()