PHP中的科学计算

i have a client that wants to turn this calculation into a function in PHP. i been given test numbers with an answer for it and i am out from this answer by too much for it to be correct im not sure if the calculation is wrong or im just not seeing the issue.

function Density($m1 , $m2, $m3, $pw, $psm){

  return   $m1 /  (($m2 - $m3) / $pw) - (($m2 - $m1) / $psm) ; 
} 
$Density = ( Density(746.2, 761.7, 394.6, (998.1*1000), (761.7-746.2)) / 1000000)

output : 2.02882553228
answer : 2.127

also i have tried it like this as well but this is way far out for it to be right

function Density($m1 , $m2, $m3, $pw, $psm){

  return   $m1 /  ((($m2 - $m3) / $pw) - (($m2 - $m1) / $psm )); 
} 

output : -0.001
answer : 2.127

i know it should be as close to the answer as it can get 0.010 out fromthe correct answer but i dont see what im doing wrong please help internet.

Remember BEDMAS - brackets exponents division multiplication addition subtraction. Your code is wrong for the order-of-operations:

m1 / (((m2 - m3) / pw) - ((m2 - m1) / psm))

or, if that equation had been typeset properly:

          m1
 --------------------
 m2 - m3      m2 - m1
 -------  -   -------
    pw          psm

Your implementation is different from the required.

You should ensure operator precedence rule is correctely observed:

return   $m1 /  ((($m2 - $m3) / $pw) - (($m2 - $m1) / $psm)) ;