Convert mixed fraction string to float in PHP - php

Question

I assumed there'd be an easy way in PHP to convert a string like 18 5/16 into the float 18.3125. I can't find a straightforward function to do it. Is there one, or do I need to write my own?

Answer 1

I don't think such a function exists -- at least not bundled with PHP.
Writing a function that does this operation, if your string always have the same format, should not be too hard ; for example, I'd say that something like this should do the trick :
$str = '18 5/16';
var_dump(calc($str));
function calc($str) {
$int = 0;
$float = 0;
$parts = explode(' ', $str);
if (count($parts) >= 1) {
$int = $parts[0];
}
if (count($parts) >= 2) {
$float_str = $parts[1];
list($top, $bottom) = explode('/', $float_str);
$float = $top / $bottom;
}
return $int + $float;
}
Which will get you the following output :
float 18.3125
And you might get something shorter with a few regex ; something like this should do the trick, I suppose :
function calc($str) {
if (preg_match('#(\d+)\s+(\d+)/(\d+)#', $str, $m)) {
return $m[1] + $m[2] / $m[3];
}
return 0;
}
Else, not bundled in PHP, but already existing, maybe this class could help : Eval Math.
Disclaimer : I have not tested it -- so not quite sure it'll work in your specific situation.

Answer 2

To expand on Pascal's example, here is a more robust solution that can handle fractions greater than 1 and less than 1.
function parseFraction(string $fraction): float
{
if(preg_match('#(\d+)\s+(\d+)/(\d+)#', $fraction, $m)) {
return ($m[1] + $m[2] / $m[3]);
} else if( preg_match('#(\d+)/(\d+)#', $fraction, $m) ) {
return ($m[1] / $m[2]);
}
return (float)0;
}
Here is some basic test coverage, useful to integrate this code with phpunit
class FractionParserTest extends TestCase
{
/**
* < 1
* #return void
*/
public function testSimple(): void
{
$qty = '3/4';
$res = parseFraction($qty);
$this->assertEquals(0.75, $res);
}
/**
* > 1
* #return void
*/
public function testComplex(): void
{
$qty = '18 5/16';
$res = parseFraction($qty);
$this->assertEquals(18.3125, $res);
}
}