Convert float to plain string representation
floating-point, format, php
Solution
Because `sprintf()` with `"%.f"` has trouble with expressions such as `"1e-8"`, some text processing may be required:
function convertFloat($floatAsString)
{
$norm = strval(floatval($floatAsString));
if (($e = strrchr($norm, 'E')) === false) {
return $norm;
}
return number_format($norm, -intval(substr($e, 1)));
}
Tested with:
3 3
1.5 1.5
-15.482e-2 -0.15482
1e-8 0.00000001
1e+3 1000
-4.66E-2 -0.0466
3e-3 0.003
Problem
SO, The problem My question is about trivial thing: how to convert numeric string to it's plain ("native") representation. That means: if numeric string is already in plain view, leave it as it is, but if it is in scientific notation, convert it. Sample: ``` "3" --> "3" "1.5" --> "1.5" "-15.482E-2" --> "-0.15482" ``` Numeric string supposed to be valid, and if it's not - then it's not a case for conversion (we're free to return null or empty string, for example). Use-case That is needed for `bcmath` because it can't work with scientific floats. Thus, they need to be converted to plain strings (asked here). So important consequence from this use-case is that numeric string can be something like `1E-300` or `1E+500`. Since we're working with `bcmath` - it's intention is to handle such things. My approach For now, I've implemented that with regex-almighty, like: ``` function parseFloat($string) { $string = (string)$string; if(preg_match('/^[+-]?(\d+|\d+\.\d*)[Ee]([+-]?)(\d+)$/', $string, $matches)) { $precision = false!==($dot=strpos($matches[1], '.')) ?strlen($matches[1])-$dot-1 :0; $precision = $matches[2]=='-' ?$precision + (int)$matches[3] :$precision - (int)$matches[3]; return number_format($string, $precision<0?0:$precision, '', ''); } if(preg_match('/^[+-]?(\d+|\d+\.\d+)$/', $string)) { return $string; } } ``` The question I feel that there should be more simple and wise way to do that. How to achieve that in more simple way in PHP? May be some tricky `sprintf()` format? Important note: I don't want to deal with precision. I want black box. Pass something numeric there - got string as output. That's all. Don't want to deal with anything else. In fact, all my regex are about calculating length & precision - so, sure, if pass them explicitly (as parameters, for example) - we cat get rid of regex. But - no, that's not what I want.