Tag: PHP

Attending PHP UK Conference 2009

Security centered design

The conference day.  We woke up early to get in queue at registration which opened at 08:30.  When we got to the Olympia Conference Center, which was about 5 minutes walk from our hotel, it was full of people.   More than a hundred people already, and we were early.  Got our badges and notepads, grabbed a coffee, and started wondering around.  There were a few sponsor stands, so we had something to do.

Honestly, I thought there would be more stands, and from companies which are closer related to web development.  We got to O’Reilly to buy some books at 35% discount (I was the first customer of the day, beta-testing the receipt issuing procedure, hehe).  Looked at iBuildings stand briefly.  Looked at Sun MySQL something to do with reporting tool something.  It was crowded over there and I had a cup of coffee in my hands, so didn’t get too close.  Saw a few people playing with Wii and some more with MS Xbox 360.  Seemed like fun.

The conference itself featured a few talks, and it was a double track, so each attndee had to chose from one of the two concurrent speeches which to attend.  Here are the ones that I went to:

  • Keynote talk: The future’s so bright, I gotta wear shades by Aral Balkan. It was a bit too lengthy for the points it made, but inspiration non-the-less.
  • Sharding Architectures by David Soria Parra.  Very interesting discussion on scaling database across several servers. Sharding technique described can be applied to much more than just that.
  • Of Lambda Functions, Closures and Traits by Sebastian Bergmann.  A look into some advanced features of PHP 5.3.  These will make writing PHP code a bit more fun, and result a bit more pleasant to look at.
  • Living with Frameworks by Stuart Herbert.  Nice, balanced look at why frameworks are important.  It was a bit misplaced though, since it was more for people who don’t yet use frameworks, while most of the audience was from the frameworks camp.
  • Myphp-busters: symfony framework by Stefan Koopmanschap.  An overview of Symfony framework, which made me love CakePHP even more.
  • Security-Centered Design — exploring the impact of human behavior by Chris Shiflett. Interesting descussion (with cool examples) of social part in security approaches.

Sharding Architectures and Lambda Functions were two of my favourite talks for technical insight.  Security-Centered Design and Living with Frameworks were the two favourites for non-technical inspiration.

After the last talk there were a few free beers at the venue, and after that there was another beer session at Brook Green Hotel.  Quite a few people, quite a few pints, quite a few interesting conversations and contacts made, excellent buffett, and overall a time well spent.

A note to conference organizers: I know you guys worked hard to make this happen, and that you are a bunch of hobbyiests who are not getting paid to do this, so, first of all, thank you.  I really enjoyed the event.  Here are a few things that I think could be improved, just in case  you will have control over them the next time:

  • WiFi coverage.  Yes, it was there and it was sort of working, but it was also slow and unstable.  At the beginning I thought that was just me for some reason, but then heard a few more people complain.
  • Power sockets.  I remember seeing only 3.   Maybe I just didn’t find them, of course, but they are sort of important.
  • Beer is the ultimate conversation maker.  Have it nearby from lunch on and more magic would happen.  (It doesn’t have to be free)
  • Mechandize.  Stickers, t-shirts, badges, etc to help remember and promote the event.
  • More stands.  I wanted to see people who do hosting, consulting, trainging, build tools, and more of the related.

As I said, I had an excellent time, learned a few new things, got inspired, met interesting people, etc.  An event was definitely a success and I’d gladly attend the future ones as well.  Oh, and I made a few pictures, which are available in my PHP UK Conference 2009 Flickr set.

Programming religions

I’m slowly catching up with the news stream and all the jokes of the last few weeks.  “If programming languages were religions” is a nice one.  Here is PHP, which I spent the most time with now:

PHP would be Cafeteria Christianity – Fights with Java for the web market. It draws a few concepts from C and Java, but only those that it really likes. Maybe it’s not as coherent as other languages, but at least it leaves you with much more freedom and ostensibly keeps the core idea of the whole thing. Also, the whole concept of “goto hell” was abandoned.

And here is Perl, which is my favourite programming language so far:

Perl would be Voodoo – An incomprehensible series of arcane incantations that involve the blood of goats and permanently corrupt your soul. Often used when your boss requires you to do an urgent task at 21:00 on friday night.

Check the rest of them for fun and profit.

Perl vs. PHP : variable scoping

I’ve mentioned quite a few times that I am a big fan of Perl programming languge.  However, most of my programming time these days is spent in PHP.  The languages are often similar, with PHP having its roots in Perl, and Perl being such a influence in the world of programming languages.  This similarity is often very helpful.  However there are a few difference, some of which are obvious and others are not.

One such difference that I came up recently (in someone else’s code though), was about variable scoping.  Consider an example in Perl:

#!/usr/bin/perl -w
use strict;
my @values = qw(foo bar hello world);
foreach my $value (@values) {
    print "Inside loop value = $value\n";
}
print "Outside loop value = $value\n";

The above script will generate a compilation error due to undefined variable $value.  The one outside the loop.

A very similar code in PHP though:

#!/usr/bin/php
<?php
$values = array('foo','bar','hello','world');
foreach ($values as $value) {
    print "Inside loop value = $value\n";
}
print "Outside loop value = $value\n";
?>

Will output the following:

Inside loop value = foo
Inside loop value = bar
Inside loop value = hello
Inside loop value = world
Outside loop value = world

In Perl, variable $value is scoped inside the loop.  Once the execution is out of the loop, there is no such thing as $value anymore, hence the compilation error (due to the use of strict and warnings).  In PHP, $value is in global scope, so the last value “world” is carried further down the road.  In case you reuse variable names in different places of your program, counting on scope to be different, you might get some really interesting and totally unexpected results.  And they won’t be too easy to track down too.  Be warned.

Oracle and PHP – the deadly mix

WI’ve spent most of the last week getting into, around, and out of the issues related to interoperability of Oracle and PHP.  Before you start laughing, cursing, and blaming, Oracle wasn’t my choice of the database for this specific project.  It’s just the company already had it installed and working for the background, and there needed to be some integration with the front, which is of course MySQL and PHP based.

First thing I do, obviously, is visit PHP.net to check for the prefix of the functions that I need for Oracle.  Through out my experience with PHP, that’s about the only thing I need to know to start working with the new database.  Oh, and the PHP module installed to provide those functions. Oracle interface for PHP is called is called OCI8.  All you need to do now is install the oci8 module.

Here comes the first trouble.  oci8 is not provided as a pre-compiled package for Fedora Linux.  There is an alternative yum repository – Remi, which has oci8 RPMs, but first of all, the oci8 module is compiled against somewhat outdated Oracle headers (version 10.2.0.4 instead of the latest 11.1.0.1), and it also needs to replace your native PHP and MySQL packages.  I tried that, and it sort of worked, but I wasn’t happy.  So I got my Fedora packages back and decided that I need to compile oci8 myself.

In order to compile oci8, one needs to download Oracle InstantClient (basic package) and some header files (devel package).  These can be downloaded from the Oracle web site, for free, minus the time for the registration.  The little trick here is that during oci8 compilation process, the includes are searched from locations which do not include the one from Oracle RPM.  I did a simple symlink of the includes folder to where Oracle headers were, and compilation went on just fine.  (Hint: otherwise you’ll get a whole lot of Zend related messages and a fatal error).  Gladly, I only had to do this path correction on the Fedora 9 machine.  My production server with Red Hat Enterprise Linux 5 compiled oci8 without any problems all by itself.

Update: more detailed instructions on the actual installation can be found here and here.

Now that oci8 installed and configured, I spent some time figuring the correct way to specify the DSN.   Oracle uses some weirdly name file (tnsnames.ora) in some weird location, but luckily there is a way to go around it.  More so, I recommend that you remove tnsnames.ora file altogether, since it can add to your troubles.  For example, if you mix spaces and tabs as whitespaces in that file, you are screwed.  So, just get rid of it.  The way you specify DSN is directly in the PHP script, and you use the syntax like so:  “//hostname.or.ip:port/dbname“.  Intuitive, I know.

Once you’ll get connected to the server, you have a whole bag of surprises waiting for you.  That is if you are too used to working with MySQL.  First is the syntax.  Oracle is using PL/SQL, so you wipe the dust of from that really old Pascal textbook that you have somewhere.  “begin :result := some.procedure.call(:param1, :param2); end;” – that sort of thing.  Secondly, you’ll be happy to know that prepared queries are supported.  So your workflow will slightly change.  Perl programmers will feel more at home here.  oci_bind_by_name() and oci_execute() are your friends here.  Oh, and while you are at, get familiar with the types of the parameters, because they are important.  And don’t forget that you’ll have to bind each and every variable in the query, or get a fatal error. And since you are learning something here, get ready for the oracle errors.  The most frequent one you’ll get would be something like “Failed to retreive the error message for ORA-12345”, where 12345 would be a number of the error.  So you’ll google for ORA-12345 and ORA-54321 and ORA-XYZZZ a lot.  But than you’ll have a wrapper library and you’ll be OK.

Update: as was noted in the comments, PL/SQL is just an option, not a requirement.  Also, most of the headaches of the above paragraph could be avoided by using one of the PHP frameworks.  I personally haven’t yet tried the framework yet, since I’d like to see things working directly first.  Especially since we are not in the test mode only.

The bigger surprise is still waiting for you though.  You are very likely to discover that OCI8 implementation for PHP is very slow.  And I do mean extremely very slow.  I couldn’t believe that it could be slow, so I went into the source code and OMG!  It is really slow.  The slow part is around fetch_all() against fetch_row().  Basically, it’s always row by row and never all, even if you tell it how many rows you need fetched.

In my case, I have the server a bit far away, and there is a possibility to get many rows back.  So even for a simple query with 140 rows in results I was getting 20 seconds execution time.  Oracle was serving results fast, the network was OK, machines on both sides were powerful and all, but it was still taking 20 seconds or more.

I am still trying to find the solution to this issue, but so far it seems that the current way I do it will be the way to do it.  And the way I do it now is the following.  Never ever run direct SQL queries.  Everything goes through a stored procedure.  The results are returned all in a single row.  And that single row has the BLOB (CLOB actually) with all results in one single XML.  Fetching works good enough to get it, and then parsing is done with one of the billion XML parsers for PHP.

In my case MiniXML worked pretty good until bigger results started coming in.  That’s when I learned an important lesson.  MiniXML parses XML with a regular expression.  PHP has a couple of settings in the configuration file that limits the size of the memory and recursion during regex parsing – pcre.backtrack_limit and pcre.recursion_limit.  If you really want to kill your server, set these to -1 (instead of default 100000) and try a regex against a 1 MB XML file.  Enjoy, cause it won’t be long before everything goes down. I didn’t feel like changing from MiniXML so we just implemented some limits in the queries and stored procedures on the Oracle side, and add a few checks in PHP fail rather than crash the system.

So, to some it up, here is my experience with Oracle and PHP from the last week:

  • I had to register on Oracle web site to download packages
  • I had to re-learn my long forgotten compilation skills
  • I had to go read some C
  • I had to step on the “re-inventing the wheel” path more than once
  • I am parsing XML when working with the database
  • I had a head ache more than twice
  • I didn’t have much fun
  • After all, it works.  Sort of.

One last point in this saga is about Googling.  Ask me any question, and I do mean any question, about MySQL.  Heck, even PostgreSQL.  And the answer is just there, on the first page of Google results.  In any human or programming language.  For any operating system.  You’ll be sorted out and working in less then a minute.   Then, try asking even the simplest of the simplest questions about Oracle and PHP.  Sometimes you’ll find something.  Some other times, you won’t.  The overall feeling I have is that not a lot of people are using Oracle with PHP, and those of them who do are in their majority not very happy.

Now I’ve joined the army.

Programming language barrier

One of the frequent things that I hear about programmers is that it doesn’t matter which language the person is using and which language you need him to use, because if he is any good he’ll learn and catch up pretty fast.  In other words, if you take a decent Java programmer and push him to write PHP code for you, you’ll only have issues for a few days.  Or weeks, at most.

I understand the reasons for this statement, but I don’t agree with it.  At least not completely.

Firstly, the reasons.  They are rather obvoius, but I’d rather stagte them anyway.  Computer Science is not specific to any programming language.  The concepts and approaches are more or less the same everywhere.  Flow control, data structures, and algorithms are not language specific.  Each language has its own best practices and recommended variations, but a bubble sort in PHP will be very similar to bubble sort in Java.   Then you need some common sense, which is also not laguage bound at all.

Secondly, the disagreement.  I think that the Computer Science theory and common sense aren’t the only things that make up a programmer.  What makes a lot of difference is experience.  Programming languages, in their practical applicatoin, are just collections of software – compilers, linkers, debuggers, libraries, IDEs, etc.  Like any other software, programming language software has bugs, undocumented features, and Days When Things Don’t Just Work.  It’s the experience with the language that teaches the programmer how to handle the issues of each software piece.  And that experience is priceless (almost).

Even if you’d manage to push a Java programmer into writing PHP code, that would a waste of resources.  A Java programmer is a Java programmer, not PHP programmer.  He will, of course, learn PHP nuances with time, but, he’ll probably lose a part of his priceless (almost) bagage.  Sounds a lot like misuse of resources.

Another part of my disagreement is not so much reasoned as emotionalized.  I’ve seen a few C and Java developers switch to Perl and PHP for their new positions.  Not that I was forcing them to or anything, but they did.  And the switch was moslty painful to say the least.  Here are some of the areas that I noticed as being hard to comprehend.

Compiling vs. interpreting. Those people who were used to their compilation process were missing something for the first few days.  Some needed as much as a week to adopt, even though write-save-reload browser was done a few hundred times a day.

Debugging. There are two major camps here.  In the first one are all those people who live in the debugger.  They know all the keyboard shortcuts and they have their highlighting customized.  In another camp are people of the simpler nature, those who use print() and die() for most of their debugging needs.  It seems that most people coming from C and Java prefer the debugger way.  Most of the interpretted languages do have either a standalone debugger or a built in debugging tool, but it seems that the majority of interpretted language crowd use the print() and die() approach.

Sigils. If you don’t know what a sigil is, read this Wikipedia page.  Because you do know what it is.  Many strong type language don’t use any sigils.  Most of the loosely typed languages do.  Furthermore, when both the language from which you are changing and the language to which you are changing use sigils, chances are there will still be a difference.  PHP, for example, uses $ for both scalars and arrays.  In Perl though, you’ll get a $ for scalar, @ for array, and % for hash.  Perl’s sigils are extremely helpful when figuring out someone else’s code. I remember the pain of having just a $ in PHP, when I was learning it.  And I can’t even imagine how confusing it is for people who are used to non-sigilized programming languages.

Types. As already mentioned above, strong typed language programmers can be often confused with the fact that variables can change their type on the fly, and that they don’t even need to be declared before use.  Loosely typed language programmers will often complain about the requirement to define their types.  Three of the most common questions that I’ve heard regarding this matter were:

  • “How do I define an array of elements of a certain type of a certain length?”
  • “Is this line a piece of non-sense or does it really do something:   $sum += 0; ?”
  • “What’s wrong with writing:  int amount; amount = 2.5; ?”

There are, of course, more areas than just those – include pathes, include files, OOP, database abstraction, loops (“What the heck is foreach?”), memory management, libraries, and so on and so forth.

Even the list of the resources for each programming language takes time to build.   Yes, time.  And time is one thing that’s always against us.  Everything else we ca handle.