In an attempt to fill in some of my own, more blatant, personal voids with php, I have been searching for info on the $i, (including php.net) about what it refers to and its use, etc. As I’ve only barely touched on this before, but now we’re stretching my memory.
like for being applied to:
($i = 0; $i < 10; $i++)
Anything plain and simple that anyone could say about it?
An important note about using $i is that its use should be tightly restricted to tracking the loop index. If you’re passing it to a function then that function should call it something more meaningful such as $personIndex. That allows the function to remain more readable than if it was just $i.
Yup. It originated in Fortran, as mentioned by Felgall, where integers started with i -> N and real variables started with the rest. I was the first integer variable name.
Fortran was one of the earliest widespread programming languages, so there is quite a bit that was passed down onto the more ‘modern’ languages.
Before Fortran?
Mathematicians were using i,j,k to designate integers in algebra (subscripts, series, summations etc) long before (e.g 1836 or 1816) computers were around (this is the origin of the FORTRAN variable type defaults).
I have always understood variable i to be short hand for ‘index’ stemming from the days of C and before that, probably. ‘j’ being the next character in the alphabet was frequently used when there was a secondary loop inside the first. k would naturally follow suit.
it’s sort of the ‘standard variable’. Like X in calculus. It could be any letter, any name… the standard is just ‘i’. Perhaps it came from “Iterator”, but there’s no difference between for($i = 0; $i < 10; $i++) and for($antidisistablishmentarianism = 0; $antidisistablishmentarianism < 10; $antidisistablishmentarianism++)
I think you’ll find that using i as the loop control originally comes from Fortran where names starting with i,j,k,l,m and n are integers and everything else is floating point. That makes i the first variable name that could be used.