PHP and Constants

I have been coding in PHP for several years, and it recently struck me that I never use constants in PHP.

I tend to assign constant values to a regular variable rather than use the DEFINE ("foo", "bar") syntax.

Looking through a bunch of random scripts on my computer I notice that not many other people seem to either.

Do you folks use constants as a matter of course with PHP and should I start too?

Do you folks use constants as a matter of course with PHP and should I start too?

I never have.  Unless it's a constant built into PHP (or built into a CMS/script that I'm working with), I don't use them.

I never liked constants much - for the same reason I don't like globals.  Values should be declared in the appropriate scope, and passed to where they need to be.  I'd much rather declare a variable in a config file and pass it to my functions than make use of a constant.

- Walkere

Constants are cool for settings like your database parameters, use them only if you don't need to change the values later in your script

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I use constants too for settings in my applications (db settings, session settings, etc.)

It is cool to use them, because this way you are sure that you wont override an important variable.

I always knew they existed, what they did, what they are for and how to use them. 

The thing is I have habitual variables that I use in pretty much everything I do.  For example i use $handle for files, $dbconnect for db connection values, $sql for holding SQL  query strings etc etc

So I guess I have always used these habitual variables to store my constant values, thus I know automatically not to use them. They are my own version of reserved variables I suppose.

I do see how this is not good practise when developing products that will go to a wider community, or applications that will be potentially modified by a 3rd party in the future.

Just remembered one situation in which constants are VERY helpful.

Let's say you want to create a set of flags as options for a function.  You decide to use the bits in a number to toggle the flags on and off.

So "Flag 1" is represented by the first bit, "Flag 2" is represented by the second bit, etc.  You can define these as constants (1, 2, 4, 8, 16, etc) and then easily combine them with the bitwise "or" function...

For example...

Code:

define("FLAG1", 1);
define("FLAG2", 2);

$flags = FLAG1 | FLAG2;

if ($flags & FLAG2) {
  //  Flag 2 is set, so do whatever we need to do
}

Without constants, it becomes one heck of a headache to work with bitwise operators like this.

- Walkere

At work, we've used them for database and other credentials.

I personally don't use them on my projects.

Plus - for fun - run benchmarks against them - not that great.

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