[RESOLVED] Single Quotes and Associative Arrays

kebbelj

What's the story on single quotes inside brackets for associative arrays? Are they optional?

For instance, will $POST[formElement] always work the same as $POST['formElement']

I see the single quotes used in code examples, but I've been able to leave them off and the code still works. I can never remember seeing this issue addressed in detail in the 2 PHP books or the many Perl books I've read. (Maybe I've just been a sloppy reader.)

laserlight

If you have a constant named formElement, then by all means use $POST[formElement]. However, typically you want to access the array by a string index, so you should use either $POST['formElement'] or $_POST["formElement"].

You could read the PHP manual on arrays for more information.

kebbelj

I read the web page you listed. Let me make an analogy to see if I've got this straight. You can leave quotes off single word property values in XHTML and the page will render, but (1) it's sloppy workmanship and (2) XHTML validators will choke on it.

Leaving off the single quotes in PHP doesn't prevent the code from executing, but (1) it's sloppy workmanship, (2) future versions of PHP may reject this shortcut, and (3) it shows muddy thinking.

Why muddy thinking? There are at least three things that can appear inside the brackets: constants (no $), variables ($), and string literals. I've been lumping constants and string literals together without thinking about the distinction between them. Inserting the quote marks will remind me of this distinction every time I do it.

bpat1434

yeah, that's the one thing some people may not know. If you have constant defined, and you also have an array key that happens to be the constant name, then you are in for some trouble. E.g.:

define('formelement', 'myfield1');

echo $_POST[formelement];
// Looks for $_POST['myfield1']

echo $_POST['formelement'];
// echos out the submitted field named "formelement"

$var = 'formelement';

echo $_POST[$var];
// echos out the submitted field named "formelement"

I personally find it best to always, no matter what, encapsulate my array keys with quotes. Then I'm sure that it's not going to be mixed up somehow.

laserlight

Yes, I'd say you got it right 🙂

NogDog

Sounds like you got it. 🙂 One more reason to use quotes when using a string literal: if your application grows or you re-use the code in another application, there's a possibility that you may end up with a constant defined somewhere that happens to have the same name. If that definition happens after your use of the same name as an unquoted array index, that constant definition will fail. If the define() happens first, then you'll get unexpected results for your array value, likely resulting in a hard-to-find bug that will keep you up late into the night. 😉

leatherback

It also depends on your level of error showing: If you code with E-All all the missing quotes WILL show errors on the screen:

"Warning: Unknown contant NAME assumed 'NAME' "

So.. Low level error reporting will give you space to be sloppy. But the error DOES occur. Just use thew quotes when you are dealing with strings, the $ for variables, no quotes/$ when dewling with constants. It is the way php is defined, stick to it.

leatherback

Wow! I though I missed a whole set of posts.. Hm 4 posts within about 1 minute.. Popular thread!

Weedpacket

kebbelj wrote:
I read the web page you listed. Let me make an analogy to see if I've got this straight.

The analogy actually goes further still; HTML attribute values and PHP associative array indices both cause syntax errors if they contain spaces unless they're quoted.

$foo[may contain nuts]=true;

<div class=contains nuts>Foo</div>

both break their respective parsers, and need to be

$foo["may contain nuts"]=true;

<div class="contains nuts">Foo</div>

(And in both cases it's single or double quotes at your option!)