Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial


Lee-Ann Huber
Lee-Ann Huber
534 Points

PHP Pow() with negative exponent

Hoping someone can help me. I'm creating a mortgage calculator that works out the bond you can afford based on your salary, loan term and interest rate.

I'm struggling with the results because the exponent in the formula is negative. I know I need to use the POW() function, but I'm clearly doing it wrong as the answer comes back wrong. I'm completely new to PHP so converting this formula to PHP is becoming quite daunting for me, could anyone help? $affordability = (1-(1+$monthlyinterest)^(-$loanterm*12))/$monthlyinterest

I have it as: $affordability = (1-pow((1+$monthlyinterest),(-$loanterm*12)))/$monthlyinterest