Excel calculation in PHP

I am working on a table where some of the data is comming back directly from an api and some of it is calculated. I have an google spreadsheets sheet as an example for diffrent values and am having some trouble translating the formulas used to PHP code.

Example of a row in spreadsheets:

Note that this is just one example.

• The values I know in my PHP because I get them back from the api are A18, C18 and E18
• H18 is calculated by excel formula =AFRONDEN(((((1+(C18))^(1/12))-1)*100*1000)/1000,3) . I managed this in PHP and the value is saved in a variable
• I am trying to calculate B18, where the outcome should be 91 for this example. The formula as it is in google sheets is =-BET(H18/100,E18,A18)

I tried to use diffrent ways of calculation but ended up with really weird numbers, Also tried to investigate PMT instead of BET but with no success so far. Does someone know how to approach this?

As far as I see based on PMT, your calculation should be like this in PHP:

A18 * H18/100 * pow(1 + H18/100, E18) / (pow(1 + H18/100, E18) - 1)

This is not rounded. If you need to, use round().

Side note: If you want to use this for a real application with financial values, please keep in mind that the division operation will result in a float-value, which is not always precise.