Re: String to Variable converstion

On Wed, 17 Jan 2001, Paul Cohen wrote: > Hello all, > > I am trying to build an IRR calculator using PHP. The number of cash flow > streams I will have at any time will vary, so I am using a loop to build the > formula. Then I am iterating to solve the equation and output the solution. > > As most of you know, I am solving the following for r: > > 0=SUM SERIES(CF(i)/{(1+r)^n)) > > I can build my formula sucessfully with the following; > > $form=""; > while ($row=mysql_fetch_array($result)){ > $form.="$CF/pow((1+'$r'),$N)"; > } > > But it recognizes $form as a string, so when I put it in my "solution for r" > loop: > > for($r=-1.00; $r<=1.00; $r=$r+.0001){ > if($form>-.001 && $form < .001){ > $IRR=round($r*100, 2); > } > } > echo "$IRR%<br>"; > > > BTW, I have also tried building the $form as a variable, but since I don't > have a value for $r it just puts in zero and sets $form equal to the right > side of the equation. Therfore, instead of inserting a formula into my > "solution for r" loop, it inserts a constant for $form. > > I think my solution is to build the formula as a string and then insert it > into my "solution for r" loop, convert it back to a real formula and then > iterate for the solution. Is this possible? If not, any suggestions? > Your best bet is to write a function to do that. Look in the PHP manual for details. -- Ignacio Vazquez-Abrams <ignacio@openservices.net>