PHP Question: Octal Values

15th April 2011 - 1 minute read time

Note: This post is over a year old and so the information contained here might be out of date. If you do spot something please leave a comment and we will endeavour to correct.

Question

If I assign and print a value like this:

$a = 012;
print $a;

I get back a value of '10', why?

Answer

This is because prefixing a number with a 0 in PHP forces the number to be interpreted as an octal value. However, it is stored internally as an integer value so when it is printed we get the integer value back. To get back the original octal value you could do something like this:

print base_convert($a, 10, 8);

Or even this:

print decoct($a);

Or even this:

print sprintf("%o", $a);

PHP

Comments

Permalink

in this case if you add first zero, php will interpreted the variable as octal number and convert this value to decimal number (?) ;p

Permalink

The title of the post gave this away, otherwise you might have got me with this one :)

Add new comment

Related Content

Installing SimpleSAMLphp Using Composer

Security Assertion Markup Language (SAML) is a standard that passes authentication credentials between hosts and essentially allows for a single sign on solution to be created. The standard uses XML files that get passed between the authentication system (known as the identity provider or IdP) and the service users want to sign into (known as the service provider or SP).

Create Checksums Using The Luhn Algorithm In PHP

The Luhn algorithm was created by Hans Peter Luhn and is a way of creating a simple checksum for a number. This algorithm, also known as the mod 10 algorithm, is used in a wide variety of applications but is commonly associated with credit card numbers.

If you look at the numbers on the front of your credit card the last digit on the right is the checksum. An algorithm is done on the other numbers and if the checksum is the same then the number is considered valid.

Swapping Between Different Composer Versions

I had an issue I was trying to debug today and needed a way to swap between different versions of composer. Composer is one of the few things that I install globally so it was locked at a particular version on the machine I was using. There has been some significant changes between version 1 and version 2 and it isn't quite safe to use a composer 2 package on a platform that has composer 1 installed. As some projects I'm working on haven't been upgraded yet I needed a way to swap between versions whilst this work was being done.

Creating A Game With PHP Part 4: Side Scrolling Shooter

As another step up from the game of snake I created in my last post I decided to try my hand at creating a side scrolling shooter. Just like my other posts, this is an ASCII based game played on the command line.

A side scrolling shooter, if you didn't already know, moves a scene from right to left across the screen with enemies moving with the scene towards the player's ship, which is on the left hand side of the scene. The player can fire bullets towards the enemies so remove them from the scene.

Seeding Random Numbers in PHP

Computers are not that great at creating random numbers as the methods they use are deterministic. That is, they start from a number (called a seed) and apply maths to that number to generate pseudorandom numbers. Most random numbers generated by computers programs use a seed provided by the system, which is generally the current time. If you can guess the initial value then you can start to work out what the random sequence of numbers generated is. Most random numbers, are therefore not suitable for encryption.

PHP: Find An Array Sequence In An Array

I was looking for a function that searched an array for another array, and after not finding one I decided to write it. What I was looking for was a function that took a smaller array and searched for that exact sequence of items in a larger array. As it happens, PHP does have a number of array search functions, but they didn't produce the correct result.