Retaining Value of a Ceil-ed Function

aquastream · 02-06-2010, 07:47 AM

Okay, here's a newbie theoretical question. In other words, something I've come across which I have no idea why I would ever use but I'm curious about it anyway!

If i add a number to a variable, the answer to this becomes the new value of that variable, and if I subtracted a number from the variable, it would then subtract it from the new value rather than the original value.

For example:

<?php
$variable1 = 2;
$variable1 += 4; echo $variable1."<br />";
$variable1 -= 1; echo $variable1;
?>

However, when I use either a ceil or floor function to a float, the rounded value doesn't behave like the previous example. Instead, when I do a mathematical function to the variable, it takes it from the original value rather than the new ceil-ed or floor-ed value.

For example:

<?php
$variable1 = 3.14;
echo ceil($variable1)."<br />";
$variable1 += 1; echo $variable1
?>

Is the reason for this something to do with the fact that ceil and floor aren't pure mathematical functions like adding or squaring? If I wanted to in the previous example retain the value of the ceil (4) when adding to its value, how would I do this?

PS: Brownie points to anyone who can come up with a reason as to why I would do this in a real project.

delayedinsanity · 02-06-2010, 08:10 AM

The reason it's not acting like the first example is because you're not assigning the result of ceil().

php Code:

$var = 3.14;
echo ceil( $var ); // This just returns the result to STDOUT
$var = ceil( $var ); // This is equiv to what you were doing in the first example

aquastream · 02-06-2010, 08:59 AM

Quote:

Originally Posted by delayedinsanity

The reason it's not acting like the first example is because you're not assigning the result of ceil().

php Code:

$var = 3.14;
echo ceil( $var ); // This just returns the result to STDOUT
$var = ceil( $var ); // This is equiv to what you were doing in the first example

Simple solution to a simple problem. Why didn't I think of that! Thanks DelayedInsanity.

delayedinsanity · 02-06-2010, 10:57 AM

Simple solutions are sometimes the hardest to come by. I spent 20 minutes the other day writing a function for an application I'm developing, only to find out that it was a new function already introduced into PHP > 5.2 - the reason I found out? I gave it the same name they did.

Enfernikus · 02-06-2010, 01:51 PM

This is why you should read the docs :D

delayedinsanity · 02-06-2010, 08:33 PM

I actually do read the docs, religiously. I have a tab open with us.php.net almost 100% of the time when I'm coding, even though I've been doing this for years.

What I don't read but probably should start, is the changelog. ;)

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