Ten PHP Best Practices Tips that will get you a job

The last couple of weeks have been quite the experience for me. I was part of a big layoff at my former company, which was interesting. I've never been in that position before, and it's hard not to take it personally. I started watching the job boards, and a nice-looking full-time PHP position caught my eye, so I sent out a resume and landed an interview. Before the face-to-face portion, I chatted with the owner and head programmer on a conference call, and they ended up sending me a technical assessment quiz. One particular question caught my eye on this quiz… it looked something like this:

Find the errors in the following code:

<?
function baz($y $z) {
 $x = new Array();
 $x[sales]  = 60;
 $x[profit] = 20:

 foreach($x as $key = $value) {
  echo $key+" "+$value+"<BR>";
 }
} 

?>

So, give it a shot. How many can you find?

If you got the missing comma in the parameter list, the "new Array()" error, the colon instead of a semi-colon, the '=' instead of '=>' in the foreach statement, and the erroneous use of '+' on the echo line, then congratulations, you found all the errors! You have the basic PHP technical skills to pay the bills.

That's not how I answered the question though. I noted the errors, obviously, but I went further than that. For instance, did you notice that there were no single quotes around the array indexes ($x[sales] and $x[profit])? That won't cause a fatal PHP error, but it is a coding error! Did you also notice the use of double-quoted strings instead of single-quoted strings on the echo line? Or the usage of the opening PHP short tag? Or the usage of "<BR>" instead of "<br/>"?

After pointing out the actual errors, I made a point of adding comments about those things I just mentioned. It was enough to push the answer from "correct" to "impressive", and it scored me a lot of points with the programmers who were reviewing my application. Enough so that they offered me the job! (I eventually turned it down, as I have been seduced by the siren call of the contracting life, and I intend to flex my PHP skills to the benefit of my clients, and not a faceless corporate overlord who dabbles in telemarketing. I need a shower).

So, read on for my Ten PHP Best Practices Tips that will get you a job:

1. Single-quoted strings are your friend. When you surround a PHP string in double quotes, it is subsequently parsed by the PHP interpreter for variables and special characters, such as "\n". If you just want to output a basic string, use single quotes! There is a marginal performance benefit, since the string does not get parsed. If you have variables or special characters, then by all means use double-quotes, but pick single quotes when possible.

2. String output. Which line of code do you think runs faster?

print "Hi my name is $a. I am $b";
echo "Hi my name is $a. I am $b";
echo "Hi my name is ".$a.". I am ".$b;
echo "Hi my name is ",$a,". I am ",$b;
This might seem weird to you, but the last one is actually the fastest operation. print is slower than echo, putting variables inline in a string is slower than concatenating them, and concatenating strings is slower than using comma-separated echo values! Not only does not-inlining your variables give you a performance boost, but it also makes your code easier to read in any editor that has syntax highlighting (your variables will show up in nice colors). The little-known use of echo as a function that takes a comma-separated list of values is the fastest of them all, since no string operations are performed, it just outputs each parameter. If you combine all this with Tip #1 and use single quotes, you're on your way to some finely-tuned strings.

3. Use single-quotes around array indexes. As you saw in the quiz question above, I pointed out that $x[sales] is technically incorrect! You should quote associative array indexes, like so:$x['sales']. This is because PHP considers the unquoted index as a "bare" string, and considers it adefined constant. When it can't find a matching symbol for this constant in the symbol table however, it converts it to a real string, which is why your code will work. Quoting the index prevents this constant-checking stuff, and makes it safer in case someone defines a future constant with the same name. I've also heard that it is up to seven times faster than referencing an unquoted index, although I haven't tested this. For more on this, see the section called "Array do's and don'ts" in the Array section of the PHP manual.

4. Don't use short open tags. Eww… are you really using these? <? is just bad form. It can cause conflicts with XML parsers, and if you ever distribute code, it's going to annoy the heck out of people who have to start modifying their PHP ini directives to get it to work. There's just no good reasons to use short open tags. Use the full <?php.

5. Don't use regular expressions if you don't need to. If you're doing basic string operations, stay away from the preg and ereg function groups whenever possible. str_replace is much faster than preg_replace, and strtr is even faster than str_replace! Save those crunch cycles… your enterprise applications will thank you.

6. Don't use functions inside a loop declaration. This isn't a PHP-specific tip, but you'll see it in a lot of code.

Bad:

for ($i = 0; $i < count($array); $i++) {
//stuff
}
Good:

$count = count($array);
for($i = 0; $i < $count; $i++) {
//stuff
}
That should be pretty self-explanatory, but it's amazing how many people would rather save a line of code at the expense of performance. If you use a function like count() inside a loop declaration, it's going to get executed at every iteration! If your loop is large, you're using a lot of extra execution time.

7. Never rely on register_globals or magic quotes. register_globals and magic quotes are both old features of PHP that seemed like a good idea at the time (ten years ago), but in reality turned out to be not that great. Older installations of PHP would have these features on by default, and they cause security holes, programming errors, and all sorts of bad practices, such as relying on user input to create variables. Both these features are now deprecated, and everyone needs to stop using them. If you are ever working on code that relies on these features, get it out of there as soon as you can!

8. Always initialize your variables. PHP will automatically create a variable if it hasn't been initialized, but it's not good practice to rely on this feature. It makes for sloppy code, and in large functions or projects can become quite confusing if you have to track down where it's being created. In addition, incrementing an uninitialized variable is much slower than if it was initialized. It's just a good idea.

9. Document your code. You've heard it many times, but this can't be said enough. I know places that won't hire people who don't document code. I even got my previous job after an interview where the VP sat-in with the interviewer and I, where I had brought my laptop in and I was just scrolling through some code I had written for one of my sites. He saw my documented functions and was impressed enough to ask me about my documenting habits. A day later I had the job.

I know a lot of self-declared PHP gurus out there like to pretend that their code is so good that they don't have to spend time documenting it, and these people are full of $largeAnimal poop. Learn docblock syntax, familiarize yourself with some PHP Documentation packages like phpDocumentor or Doxygen, and take the extra time to do it. It's worth it.

10. Code to a standard. This is something that you should ask potential employers about during interviews. Ask them what kind of coding standards they use… PEAR? Zend? In-house? Mention that you code to a specific standard, whether it be your own, or one of the more prevalent ones out there. The problem with loosely-typed languages like PHP is that without a proper coding standard, code tends to start looking like huge piles of garbage. Stinky, disgusting garbage. A basic set of rules that includes whitespace standards, brace matching, naming conventions, etc. is a must-have, must-follow for anyone who prides themselves on their code quality.

That being said, I hate all you space-indenters. I mean, what the hell? 4 space characters as an indent? That's exactly four times as much whitespace to parse as a tab. More importantly, you can set your tab-stops to any value you want if you're using any text-editor more advanced than Notepad, so every developer can having something that they like the looks of. Set it to 4 if you want, or 0 if you're a masochist. I don't care, but you can't do that with spaces! You're stuck with exactly the amount that Mr. Monkey Pants in cubicle 17 decided to put in. So why are spaces so popular? This "4-space indent" standard everyone uses is stupid! Stop it! Stop doing it!

Anyway, I hope these tips are helpful. If you want to impress at a job interview, it's the little details that will get you noticed! Maybe don't rant about your coding standards though.