note 63964 added to reference.pcre.pattern.syntax

A useful note for beginners: note the difference between mathematical and PHP regular expressions. The _mathematical_ regex: (a+b+c)* which written in PHP syntax will look like: [abc]* will match any string built of a, b or c letters, but will not match string, for example: abcd However, the _PHP_ regular expression will match above string, because the regex means "accept all strings, which contain 0 or more occurences of letters: a, b or c". To convert the regexp from the mathematical to PHP convention, use the ^ and $ characters, which indicate start and end of tested string. So the regexp: ^[abc]*$ means "match all strings, which, between its beginning and end, have 0 or more occurences of letters a, b or c" - which is, what we searched for. Nasty habit, especially after two tests on "theoretical basics of computer science" :) ---- Server IP: 195.136.184.34 Probable Submitter: 87.105.48.179 ---- X-Spam-Status: No, hits=3.1 required=5.0 tests=DATE_MISSING,FROM_NO_LOWER autolearn=no version=2.64 ---- Manual Page -- http://www.php.net/manual/en/reference.pcre.pattern.syntax.php Edit -- http://master.php.net/note/edit/63964 Del: integrated -- http://master.php.net/note/delete/63964/integrated Del: useless -- http://master.php.net/note/delete/63964/useless Del: bad code -- http://master.php.net/note/delete/63964/bad+code Del: spam -- http://master.php.net/note/delete/63964/spam Del: non-english -- http://master.php.net/note/delete/63964/non-english Del: in docs -- http://master.php.net/note/delete/63964/in+docs Del: other reasons-- http://master.php.net/note/delete/63964 Reject -- http://master.php.net/note/reject/63964 Search -- http://master.php.net/manage/user-notes.php