PHP slightly increment value based on number of decimals - php

Question

I am trying to slightly increment a value based on the number of decimals it has.
For example if the value is 1.2 I would increase it by 0.1, 12.345 by 0.001, 12.345678 by 0.000001, etc.
I currently have a long implementation using a chain of if, else if. I know this is not the most efficient way and a loop can be used, but I was unsure of how to structure the loop. I tried using the PHP substr_replace function, but I could not get it to work for this.
Is there another way I can structure a loop to reduce my lines of code and be more efficient?
Here is my php code so far:
$valueOne = 12.345678;
// get amount of decimals
$decimal = strlen(strrchr($valueOne, '.')) -1;
/*
this also works for finding how many decimals
$test = floatval($valueOne);
for ( $decimal_count = 0; $test != round($test, $decimal_count); $decimal_count++ );
echo $decimal_count;
*/
// see value before change
echo $valueOne;
if ($decimal == "1") {
$valueOne = $valueOne + 0.1;
}
else if ($decimal == "2") {
$valueOne = $valueOne + 0.01;
}
else if ($decimal == "3") {
$valueOne = $valueOne + 0.001;
}
// etc ...
// see value after change
echo $valueOne;
/*
i tried messing around with using a loop, but did not have much luck
$start = 0.1;
$count = 0;
$position = 2;
while ($count != $decimal) {
echo substr_replace($start, 0, $position, 0) . "<br />\n";
$count++;
//$position++;
}
*/

Answer 1

Get the number of digits after the decimal. Then create a number with a decimal point, one less 0, followed by 1, to get the amount to add.
$valueOne = 12.345678;
// get amount of decimals
$decimal = strlen(strrchr($valueOne, '.')) -1;
// see value before change
echo $valueOne . "<br>\n";
// Get amount to add
$increment = '.' . str_repeat('0', $decimal-1) . '1';
$valueOne += $increment;
echo $valueOne;

Answer 2

Get the number of decimals
Multiply by the appropriate factor so the number is now an integer
Increment by 1
Divide by the same factor to get back to the original number (properly incremented)
function increment($number){
// get amount of decimals
$decimal = strlen(strrchr($valueOne, '.')) -1;
$factor = pow(10,$decimal);
$incremented = (($factor * $number) + 1) / $factor;
return $incremented;
}