CSE 134A
Discussion section
Friday, 11/9/2002
TA: Greg Hamerly

Hi!

Today we will discuss problems 3 and 4 from Wednesday's midterm, and using PHP
regular expressions to extract information from strings.

Project 2 will be graded and handed back on Monday during office hour. Monday is
a holiday, so there will only be one office hour (4-5PM).

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Exercises in regular expressions: work on these in groups.

(1) What do the following regular expressions extract? What will be the value of
the variable $match after each expression executes, assuming that $str has the
patterns we are looking for?

    (a) ereg("UCSD is a very ([^ ]+) school", $str, $match);


    (b) eregi("<title>([^<]+)</title>", $str, $match);


    (c) ereg("(A[[:digit:]]{8})", $str, $match);


    (d) ereg("function +([a-zA-Z_][[:alnum:]]*) *\(", $str, $match);


(2) Write regular expressions using PHP functions to *extract* the following
items from a string $str:
    (a) A Social Security number using this format: 123-45-6789




    (b) The target and textual description of a URL. For example, extract
    "http://www.google.com/" and "Google" from this string: 
        "Please click here: <a href="http://www.google.com/">Google</a>..."




    (c) The last HTML tag in a document (where you may assume the entire
    document is in the variable $str).




    (d) A number between 1000 and 2000 (inclusive).




Notes:
    - Remember these special operators when using regular expressions:
        [], ^, $, ., |, *, +, (), {}, etc.
    - There are many useful functions in PHP for regular expressions, including
      ereg(), eregi(), ereg_replace(), split(), join(), and Perl-style regular
      expression functions like preg_match(), preg_match_all(), preg_replace(),
      etc.