Math & Number Handling in PHP – The ABCs of PHP Part 6 Page 3

Back to the barrel shifter

As you can see from the above examples, each column in a
binary number is a multiplication of 2. The barrel shift,
shifts binary bits in a number left and right and as a
result is able to multiply and divide by 2 extremely fast.
This is very handy if for example we are working with binary
streams (such as if we where doing heavy number crunching in
a compression system), and if we are chopping up and packing
numbers.

Again, if this is a subject that interests you then there
are many white papers and educational texts available that
cover number theory, just be aware that if your divisions
and/or multiplications are powers of two, or if you need to
isolate only a single bit in a number then using the barrel
shifter is an extremely efficient way to do it.

Number comparisons

In any computer language, the ability to check numbers that
are in a given range is a must. You saw it earlier in the
example of a for loop, and like loops in general we’ll cover
decisions in more detail when we cover loops and decisions
in a later article, for now though we check ranges by using
the following operators:

• $a
• $a > $b; // Is $a greater than $b
• $a => $b; // Is $a equal to or greater than $b
• $a =
• $a == $b; // Is $a equal to $b

Normally you would use these in an “if” statement similar to the following:

	if($a > $b)
	{
		// Do stuff if a is greater than b
	}
	else
	{
		// Do stuff if it's not
	}

Summary

In this episode we’ve looked at basic math operations in
PHP, and had a recap on binary. As with strings and text
there is a huge number of functions that operate on numbers.

There are functions to generate random numbers, or do
complex math using sines & cosines.

As always I encourage you to look at the appropriate
sections in the PHP Manual, and
experiment with what you find there. Remember half of the
fun of programming is breaking things, then learning how to
fix them.

Until next time
Shawty

The ABC’s of PHP

Introduction to PHP
What do I need to make it work?
Basic Script Building in PHP
How Variable Am I?
Strings & Text
Math & Number Handling in PHP
Introduction to Arrays and Hashes in PHP
Loops and Decisions in PHP
Advanced String Processing – How Regular Are Your Expressions