PHP Recursive Function

As a self-taught PHP developer with no training, I was recently embarrassed that I could not write a recursive function.

Recursive Function: A function that refers to itself.

Recursion: Something that refers to itself.

What is recursion for? I'll do my best to explain this. Often there are things that can be done either by iteration (like a simple loop that keeps adding one) or by recursion (its a loop, but it functions a little differently). True recursion always has an end or reaches a final value.

Here's a simple example of an 'iterative' loop. Let's say you're trying to find the factorial of 7, written as 7! (which means, 1*2*3*4*5*6*7). Here's an iterative loop to do this:

‹?php
function myfactorial($input) {
$result = 1;
while ($input > 0) { $result *= $input; $input--;}
return $result;
}
?›

now we can run the function:
(add this line after the function)
print myfactorial(7);
the result we get is 5040

There's another way to calculate the factorial. It is a loop, but it's recursive, since the function refers to itself. Effectively we keep multiplying the function total smaller input numbers until we reach 1, then we stop. In other words, myfactorial(7) starts at a value of 7, which we multiply by 6, then we multiply the result by 5, then by 4, etc. This does the same thing as the function above, but it does it recursively

‹?php
function myfactorial($input)
{
if ($input < 2) {return 1;}
else {return ($input * myfactorial($input-1));}
}
?›

Now we can execute this function:
(add this line after the function)
print myfactorial(7);

the result we get is 5040

So what good is recursion in real life? I am still working on that. Some say the idea of recursion somewhat references 'divide and conquer'. Basically, recursion represents an algorithm... perhaps even a very simple algorithm. Recursion can be used to break down complex problems down to a simple common denominator. Once you remove all the simple instances of an algorithm from a complex problem, sometimes you are left with something very small and simple. Apparently the programming language LISP is tuned for recursion, and apparently most functions in that language use recursion...

Why is the Linux Logo a Fat Penguin?

Linux is light, flexible and fast. Shouldn't the Linux logo portray that? The penguin logo really doesn't make any sense to me; its not light, flexible, or fast either. If anything, it represents several things that really don't describe Linux in any way, shape or form.

If any operating system needs a 'fat' mascot, it's windows... Like, how about we switch from the windows logo, to a giant bloated whale... I admit I use windows 7 on a laptop, but honestly, I am afraid to switch due to driver issues. Aside from that, it's got a Core i7 processor, so only Vista/ Windows 7 can really fully utilize the set of 8x virtual processors (Windows 9.x and XP Pro can't). By the way, I apologize to hardcore Linux fans, for mentioning Windows...

Anyway, back to the Linux, fat, happy penguin... Honestly, something like an antelope, cheetah, or whatever makes more sense... To me a penguin just doesn't really describe Linux. Yes a penguin is small-- (ok, linux doesn't take as much memory as windows, it's sort of small). BUT, a penguin is also fat, and not very agile (at least out of the water)--and most definitely not flexible (ever seen a penguin walk?). Linux is agile & flexible, due to the myriad of ways you can customize the open source operating system. On the other hand, Windows is not flexible at all; it's closed source and your degree of control is nothing compared to Linux.

With Linux you can customize the Kernel, add or remove almost anything, and you can set the OS to leave almost all of your resources free (any webmaster knows how light and responsive Linux servers are compared to Windows servers). Maybe, the Linux mascot should be a ghost... because hey, what's lighter than a ghost? The only problem with that, is that ghosts are dead (well, ghosts are alive, but represent people that have moved on). Also, the truth is, Linux is alive and well--so I guess that shoots down the whole ghost idea (although I'm sure Bill Gates would love to see the Linux die!)

So how about a new mascot for Linux? Is anyone with me on this?

UnInstalling Kaspersky from Plesk at the Command Line

Why Remove Kaspersky from Plesk?

Parallels Plesk Panel Anti-Virus Powered by Kaspersky

As you may be aware, Kaspersky anti-virus protects users that visit your webserver from getting infected by viruses. Perhaps the primary use of Kaspersky in Plesk is to protect your linux mailserver from spreading viruses.

Unfortunately, Kaspersky Anti-Virus for Plesk is a paid service. Some of us are on a budget and we can't afford it. If you're like me, you'll want to uninstall it.

How to Uninstall Kaspersky From Plesk

I've taken a close look at the server settings in Plesk. Most modules can't be removed, or even disabled via plesk. It's one of the limitations of Plesk, even in version 9.5.2 (the most current version of Plesk at this time). Since a GUI solution is not an option, you'll need to reach your server by command line (via SSH).

Removing Kaspersky from Your Plesk Server via Command Line

Personally, I use putty to reach my server by SSH. I also use SSH for file transfers (instead of FTP). In fact, I don't even allow FTP access on my server. This closes a lot of potential security holes...

Reach Your Remote Server via SSH

To reach your server via putty, you'll need to input your IP and port (generally SSH is on port 22). Once you reach your server you need to log in to your server with your root user and root password. Of course, if your server is local, just log in, then get to the command line.

How to Copy and Paste in PUTTY

If you want to paste your password directly into the putty interface use SHIFT + Insert (to paste). Just as an FYI, SHIFT + CTRL is the command to copy (alternatives to CTRL-C and CTRL-V to copy/ paste). The putty interface uses old-school commands--although CTRL-C does work in putty, it will also 'stop' anything currently in execution (CTRL-C was the default to stop things from running during the dark-ages of computing). Anyway, this is why the SHIFT-Insert/ Shift-CTRL options are best for copying and pasting in putty.

Uninstalling Kaspersky for Plesk Via Command Line

This here is for linux machines (just an FYI). Some common linux variants are Fedora, RedHat, CentOS, LinuxMint, Ubuntu, Debian, etc. Anyway, here are the commands you will need:

First, query via RPM to find the exact name of your installed kasperky plesk package.
[root@(your ip)]# rpm -q psa-kav
(my result:) "psa-kav-1.0.0-cos5.build95100504.12"

Next, use the exact name from your query with "rpm -e" to uninstall kaspersky:
[root@(your ip)]# rpm -e psa-kav-1.0.0-cos5.build95100504.12

Here is my result for running the above command:
Trying to start service mysqld... done
Trying to establish test connection... connected
done
Trying to unregister mailhandler... done
Trying to unregister service aveserver... aveserver couldn't be stopped
using /sbin/chkconfig
===> Unregistering module
Trying to start service mysqld... done
Trying to establish test connection... connected
done
===> Uninstalling database
Trying to remove user kluser... done
Trying to remove group klusers... done

Great Success

Great, now kaspersky is uninstalled. If you're still set on having an anti-virus on your server, I recommend Clam Antivirus. A simple yum install via SSH (command line) can get you up & running with Clam (assuming fedora, centos, or a redhat server). Your server might require an app-get or something like that (other linux flavors). I have yet to install & configure clam. If I do, I'll be following up with a new blog on the subject.

And as usual, have a craptastic day!

Masters in Business Administration (MBA) vs Masters in Computer Science (MSCS)

MBA vs MS Computer Science

I took the question seriously and did some research and maybe a little soul-searching too. So what's best? MBA vs MSCS Here's my conclusion:

MS Computer Science

An MS in computer science is time sensitive. Once your degree is 20 years old, it doesn't hold much value. To stay current and valid, an MSCS (masters in computer science) needs to get certifications and complete ongoing education. Right now, there are massive layoffs in the technology sector. Older companies like Sun Microsystems are laying off lots of people with 20+ years of experience in technology. Supposedly lots of these people are computer science graduates. Sure google & facebook are hiring fresh grads, but more experienced people in the industry are getting laid off just as quickly.

(Assume education at an elite school) Immediately after graduation, an MSCS can earn $100k per year (+/-15k), while only working 50 hour a week in a cushy environment where they can dress casually and play billiards or other games during their breaks. Right now there is a big push from google & facebook to hire all the best graduates--so computer science salaries at the entry level are on the rise. However, I have read claims that long term computer science salaries are going down.

The large number of layoffs, and falling salaries at senior levels (in some cases) explains why the number of MSCS graduating every year is going down! Apparently, the salary ratio 20 years ago was 2.5x -- you could earn 2.5x your entry level salary eventually with an MSCS. However, today, the ratio is only 2.0x--you can expect to earn less than your MSCS predecessors did once you reach senior levels of experience.

MBA

An MBA from an elite school can lead to a job as an investment banker, strategy consulting, private equity, corporate finance, or other management roles. There are limited positions in Ibanking, Private Equity, and Strategy Consulting, and they are almost completely filled by just a few of the top schools. Probably the most rewarding work is in private equity--apparently, graduates from schools like Wharton that are lucky enough to get hired by private equity can expect salaries of $500k to $700k per year (and up).

Most MBA graduates agree that the networking which an MBA creates is substantially more valuable than the actual education. The reason is, if you go to a school like Havard, or Stanford, you can expect that most of your classmates will be successful executives in 10 to 15 years. MBA schools create some strong bonds between students who see themselves as being part of a very special elite group. Just an email or a phone call can easily re-ignite these old relationships--and being alumnus from the right school can and does often lead to great job or venture opportunities.

There are probably those that might somewhat regret earning an MBA. I would venture to say that very few of those people went to top schools; the salary curve heavily favors graduates of top schools, and so do the opportunities. Right now, the number of MBAs is growing annually. People have seen the gravy train and they want a ride. However, some don't understand that an MBA from a poorly ranked school is a commodity. The true value of an MBA is the networking and the reputation you gain from going to a top MBA program. Without that, the MBA is not worth much at all. In fact, supposedly (according to some bloggers), the actual education for MBAs is actually quite outdated at many schools. While case studies do help with problem solving skills, what you learn, ends up being less important than where you learn it (hopefully a top MBA school) and how you learn it (team environment).

MBA vs MSCS

An MBA usually requires 3 to 7 years of experience depending on the school attended. An MSCS requires nothing other than a bachelors. MBA admissions expect well rounded, experienced, potential future leaders, with good test scores and grades. With an MSCS, no experience is required. MBA students participate heavily in a case study, team environment which creates a lot of bonding, and a lot of long term loyalty. An MSCS is a student of science, and the case study environment simply is not used (not the MBA format at least).

An MBA is the only way to get into the top strategy consulting, investment banking, and private equity jobs. However, it is also seen a mark of approval, or a sign that you're one of tomorrows future business leaders. Admittedly, a lot of these top jobs are truly horrible careers that pay very well, and take all of your time (and perhaps some of your 'life essence' too)--e.g. investment bankers should expect to work 80hrs+ per week. An MBA is the possibly the best degree to have if you want to go places in the business world. On the other hand, an MSCS is one of the best degrees to have if you want to go places in the technology world.

An MBA is like fine wine, because it becomes more valuable with age--that is if you build an excellent network of associates, your MBA could be your connection to CEOs and executives at top companies around the country. An MSCS is like milk that quickly becomes stale with age. An MSCS loses value as time goes by, as the knowledge you've gained, slowly becomes outdated (unless the MSCS works on certifications and education on an ongoing basis).

Sure, some of that theory knowledge is still great, but 20 years in technology feels like more than 100 years in the real world (i.e. a generations passes every few years in technology). Technology goes through a generation at least once every 10 years... Sure, the fundamentals in many areas stays the same, but the constant change can be difficult to cope with. The advantage that the MBA has, is that the knowledge itself is not what is valuable; its the networking & the reputation you gain (assuming you go to an 'elite school'). An MSCS from an elite school will surely still hold some reputation in 10 or 20 years. However, MSCS students are less likely to bond and network like MBA students-simply because they are not in the MBA case study / team environment.

Anyway, I think if a person loves technology, they can & will take that big risk with computer science. And if you love money *cough* business, you can & will take that risk with an MBA. In truth though, an MBA from an elite school with 20 years of experience doesn't seem a likely layoff candidate. And even if an MBA does get laid off, they can fall back onto their network of friends and alumni. While in fact, people with 20 year old MSCS degrees are getting laid off even as I am writing this. An MSCS will surely have some friends and acquaintances from their schooling, but it's just not the same level of networking and bonding that an MBA builds.

An MSCS is a good ticket in the near future to a cushy, well paying job. An MBA leads to elite jobs, many of which pay in the stratosphere, but they also require a commitment in the stratosphere. However, an MBA can also lead to many excellent cushy corporate jobs--although probably not as cushy as MSCS jobs. An MBA can potentially become more valuable with time, while an MSCS slowly becomes outdated. If you love programming, then an MSCS is worth the long-term risks. It is really difficult to gain entrance to an elite MBA school, due to the combination of requirements in leadership experience, grades and test scores. I'm sure it's not easy to get into a top computer science program either. But, an elite MBA program is definitely the harder of the two to enter. While MBAs from poorly ranked schools are commodities, an MBA from a top school is truly a treasure.

Summary

An MBA from a top school is like an entrance ticket to an excellent career in business. It's no guarantee, it's an investment, and like any investment there are associated risks. An MSCS is the same, except it will lose value with age, and its simply not valued as highly as an MBA (probably due to a general lack of real life experience in most graduates). Top MBA school graduates in 2009 could expect $150k per year on average, while top MSCS graduates could probably expect $110k per year on average. Long term an MBA appears to be a better choice, except for the fact that an MBA doesn't give you any actual skills. In contrast, an MSCS will help you gain some real skills related to software development and programming. If you don't mind being laid off in 15-20 years, an MSCS is an excellent ticket to enter a cushy software development job. If you don't mind the fact that an MBA gives you no actual skills, and many people will view you as overpaid, then an MBA is an excellent foundation for a successful business career.

And as usual, have a craptastic day!

Fedora Does Not Work Without Yum And Python!

Remote Dedicated Sever OS Upgrade: Linux Fedora 7 to CentOS 5.3

Prepare for Linux OS upgrade, Back up Plesk

Pre-Update Preparation: backup all critical files locally. If you use plesk, you can use the site backup & server backup functions to back everything up. All the plesk backup files are stored in:

/var/lib/psa/dumps/

(the official link for information on plesk backups)
http://kb.parallels.com/en/6082

Old versions including plesk 8.0 and earlier will store your backups in numbered files
Newer versions including plesk 9.0 and later will store your backups under 'clients'
Full server backups appear to be stored in the root directory.

Getting Plesk to Recognize Your Backups

Warning for this with large backup files: Plesk wont let you restore anything until all the files are in place on your new server. So you may have to do a lot of uploading before you can finally restore things.

You'll notice some .xml and .tgz files among your backups. Here's something important: you may want to clean out /var/lib/psa/dumps/ before you run your backups. I had 17 gigs of backups, most of which are completely useless--partly because my server was several years old. This way, when you SSH into your server & download your files, you wont be grabbing many gigs worth of useless information. The XML files have dates and other key information stored about your configuration & backups. The .tgz files have data.

Fedora Core 7 to 8 Upgrade Issues

Today I upgraded my server from an older OS to a newer one (Linux Fedora 7 to CentOS 5.3). I was fighting with Fedora Core 7, and slowing working my way to Fedora Core 13 (you can't do it all at once, the versions are too far apart--I learned a long time ago, its always safer to go one version at a time with anything related to linux!). My server decided it was schizophrenic and was requiring multiple versions of python (2.4 and 2.5) at once. Yum was displaying dependency conflicts that could only be resolved if I had BOTH python 2.4 AND 2.5. There are ways of supporting multiple python installs at once, but its really ugly, and theres a chance you could over-write your primary python installation if you're not careful. I made the mistake of completely uninstalling YUM and PYTHON--because it seemed the only way to resolve thigns-- yes believe it, I did it.

Yum Uninstall Python: Warning!! Do NOT Press This Button!

If you know anything about Fedora, uninstalling YUM and PYTHON is like taking a rowboat out into the middle of the ocean, poking a hole in the bottom, and throwing away the paddles. Fedora CANNOT function without YUM and Python!! Well, there's a few minor exceptions-you can manually compile things, but without YUM & Python its easy to make mistakes. YUM install is critical and is probably the fastest and easiest way to resolve dependencies and get things up to date. I actually managed to find a tar.gz version of Python 2.5 and restore it to the server. (I had to unzip the tar file & manually compile it with .configure / make/ make file/ etc.

I was thinking of then re-installing YUM but then I decided it was better to throw in the towel. My server had been hacked over 5 years ago when I was a newbie server administrator. The hacker had actually come in through an operating system loophole-- a vulnerability that allowed them to log in without needing to know the root password. Since then I have kept my servers safe by blocking all IPs except ones absolutely necessary. There are 2 ways of doing this. 1-use iptables (no thanks) 2-use plesk to configure IPtables for you (easy)

Configuring Plesk Firewall (Easy IP tables Updating)

You can configure plesk firewall by going to modules > firewall > edit. if you don't see a firewall installed, you can go to home > updates > (chose your current version), find your option for a firewall & install it. if a firewall option is greyed out, you might have an issue with your plesk key. Did I mentioned that I was only able to put 1 single domain on my server without restoring my plesk key? With my plesk key, the limit is 30 domains (a major difference....)

MySQL User Issues Made Wordpress Look Like it Was Failing (Solved)

I had a wordpress installation on my plesk centos 5.3 server. Once I restored my sites from plesk, I found out NONE of them worked. Here's the issue: when you restore a website backup with plesk backup manager, plesk does NOT set up permissions for the users! So here's how you grant your old MYSQL users permission through plesk: simply remove each user, and add each user back (with the same password(s)). Plesk will automatically give each user permission to the respective database, with the respective domain & client. After that, everything worked perfectly. I should mention; I did make an update to vhost.conf, but I have no idea if it helped. I made the update because it appeared that the php 'includes' or 'require' functions were not working. It seemed PHP did not have permission to open files on my own server!

Editing vhost.conf to Fix open_basedir Issues

php_admin_value open_basedir "/var/www/vhosts/yourdomain.com/httpdocs:/php/includes"


Once you make the change & save your new vhosts.conf file, you'll need plesk to reconfigure things. The easiest way is to just rebuild all your sites:

Command to Make Plesk Recognize vhost.conf Changes

/usr/local/psa/admin/bin/websrvmng -a

Fedora Does NOT Work Without Yum or Python!

Anyway, I learned a very tough lesson today. Fedora does NOT work without yum & python. I mean, you could rebuild python from scratch, but if you yum uninstall python, you're going to break your server--and if you're connected remotely, you're screwing yourself! So be careful people. Don't forget--yum is dependant on python. Don't remove python unless you truly know what you are doing, otherwise, you're in for a world of pain. (You'll probably botch your install and need to start from scratch).

And as usual, have a craptastic day!

Add SRware Iron to CCleaner

If you've heard the news, there's a new great browser called SRware Iron. Basically, it's an exact clone of Google Chrome, except for one area. ALL of the privacy invasion software that Google Chrome uses to abuse your privacy have been removed.

Now, I depend on CCleaner to quickly clean up excess programs on my hard drive. It's free software written by Piriform, and I find that it's an excellent and safe tool. Unfortunately, there is no support for SRware Iron right now.

Here is the official site for SRWare Iron (A Google Chrome Clone)
http://www.srware.net/en/software_srware_iron.php

Here is the official site for CCleaner http://www.piriform.com/ccleaner

Generally I use CCleaner to wipe unnecessary temporary files off my hard drive before I make a full backup with a program such as Norton Ghost.

Unfortunately, CCleaner is not built in with SRWare Iron support... yet. So here are some quick instructions to add SRWare Iron to CCleaner.

1-Figure out where CCleaner is installed on your hard drive. The default folder is: C:\Program Files\CCleaner

2-Create a file named "winapp2.ini" in this directory: C:\Program Files\CCleaner

3-add all the information below to your "winapp2.ini" file (you may note that a ";" semicolon denotes a comment line in your "winapp2.ini" file, which means CCleaner will ignore that particular line. You don't need to include any line that starts with a semi colon, and in fact, you can make up your own comments, as long as the line starts with a semi-colon.

; Piriform CCleaner: winapp2.ini application cleaning file add-on
;
; Notes
; ---------------------------------------
; LangSecRef
; 3021 = Applications
; 3022 = Internet
; 3023 = Multimedia
; 3024 = Utilities
; 3025 = Windows
; 3026 = Firefox/Mozilla
; 3027 = Opera
; 3028 = Safari
;
; IMPORTANT INFORMATION:
; If you make any cleaning entries that drastically slow down
; CCleaner removing them will allow CCleaner to function faster.
; Also removing cleaning entries for software you no longer
; use or have installed will allow CCleaner to function faster.


; SRWare Iron starts ------->
[Cache]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default\Cache|*.*

[Cookies]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Cookies

[Internet History]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|*History*
FileKey2=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Thumbnails
FileKey3=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Visited Links

[Current Session]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Current*

[Last Session]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Last*

[Form Data]
Section=SRWare Iron
DetectFile=G:\Program Files\SRWare Iron\Iron.exe
Default=True
FileKey1=C:\Documents and Settings\blink\Local Settings\Application Data\Chromium\User Data\Default|Web Data
; SRWare Iron ends ------->

4-if you don't see SRWare Iron added to your CCleaner options, it means there is a mistake. You can try & edit/ replace C:\Program Files\ with %ProgramFiles%\ and you can try & replace C:\Documents and Settings\ with %Documents and Settings%\ (this is where user settings are stored in all versions of windows xp ). if you're using windows vista or windows 7, you'll need to replace C:\Documents and Settings\ with something like this: %userprofile%\

5-Important!: CCleaner is pretty fickle with settings in winapp2.ini -- it's case sensitive and it needs the exact settings on your machine. If nothing shows up in CCleaner, it means you've got one or more of your settings wrong. Check for upper or lower case, check the files paths..

If all else fails, you can check the official ccleaner documentation. Be forewarned, the official documentation had a few mistakes and was out-dated as of May 27, 2010

http://docs.piriform.com/ccleaner/advanced-usage/ccleaner-ini-files/how-to-add-your-own-program-for-ccleaner-to-clean

Why Did I Write This: This is a quick reference for me, as much as it is to help others. If you feel like this information is useful, please don't hesitate to comment.

And as usual, have a craptastic day!