out of memory issue with PHP script - php

Question

My PHP script is running out of memory. I have put memory_get_usage( ) inside the loops and found that it is running out of memory after 6MB.
I would like to clearly explain my script and like to get suggestions from you.
I am not sure, If my script is running out of memory because of problems with code .
So, here is the algorithm for my script:
Read the input json data into an array ( approximatley 200 lines of data)
calculate the sum of the array ($sum)
3 variables $starting, $ending and $compare.( Intialize $compare = $starting)
start with $starting=$vmin , calculate scaling factor, scale the original array and calculate sum of it .That new sum is $ending.
Add 10 to $starting until the diff between $ending and $compare is 50.
repeat all the steps until $vmin reaches $vmax with an increment of $vinc
The above algorithm might look insane, But it finds an optimal solution for supply chain related optimization problem.
I would like you to see if my weak coding capabilities are the reason for the memory outage .If so, Please suggest the changes to my script.
Here is my code
$vmax = 10000;
$vmin = 1000;
$vinc = 2000;
//decode the json data
$fp = fopen("data_save3.json", "r");
$inp=file_get_contents("data_save3.json");
fclose($fp);
$inp=json_decode($inp);
//calculate the array sum
foreach($inp as $i=>$element) {
foreach($element as $j=>$sub_element) {
$sum+= $inp[$i][$j];
}
}
//start at vmin and increment it until vmax
for(;$vmin <=$vmax;) {
$starting=$vmin;
$compare = $starting;
//calculate scaling factor
$scale = $starting/$sum;
//calculate the scaled array
$sum2 = 0;
$inp_info2 = $inp;
$ending = newscale($inp_info2,$scale,$sum2);
$optimal = getClosest($starting,$ending,$compare,$sum);
echo $optimal.PHP_EOL;
$vmin = $vmin+$vinc ;
}
// function to find the closest value
$inp_info1=$inp;
function getClosest($starting,$compare,$ending,$sum,$inp) {
global $sum2;
global $compare;
global $inp_info1;
global $starting , $ending, $scale1, $sum, $inp, $inp_info2, $inp_info3,$rowsum2, $rowsum3, $rowsum4, $rowsum5;
if (abs($ending - $compare) < 50){
return $starting;
} else{
$starting = $starting +10;
$scale1 = $starting/$sum;
$inp_info1 = $inp;
$sum2 = 0;
$ending = newscale($inp_info1,$scale1,$sum2);
return getClosest($starting);
}
}
//array scaling function
function newscale($array,$scale,$sum2){
global $sum2,$scale;
foreach($array as $i=>$element) {
foreach($element as $j=>$sub_element) {
$array[$i][$j]*= $scale;
$array[$i][$j] = truncate($array[$i][$j]);
$sum2+=$array[$i][$j];
}
}
return $sum2;
}
//truncate function
function truncate($num, $digits = 0) {
$shift = pow(10, $digits);
return ((floor($num * $shift)) / $shift);
}