How to keep two digits in float number (PHP)

Question

How to make number like 3.0000000054978E+38 to 3.00 in PHP?

Many thanks!

`round()` it http://us3.php.net/manual/en/function.round.php — Michael Berkowski, May 01 '12 at 12:44
You have not shared the criteria how to make `3.0000000054978E+38` to `3.00`. Normally that is done with multiplication/division. — hakre, May 01 '12 at 12:57

score 2 · Answer 1 · answered May 01 '12 at 12:51

2

You cannot use round to solve this since it is a number in scientific notation. You can, however, use substr:

$i = 3.0000000054978E+38;
$i = substr($i, 0, 2); // $i is now the string 3.00
echo( number_format($i+1,2) );  // Will output 4.00

answered May 01 '12 at 12:51

Jeff Lambert

Round does work for scientific notation. There's nothing wrong with round and floats. – hakre May 01 '12 at 12:56
`$i = 3.0000000054978E+38; echo( round( $i, 2) );` That outputs 3.0000000054978E+38 on Windows, not 3.00 – Jeff Lambert May 01 '12 at 12:57
@Watcher: Sure, because it does what it has been documented for. But it's obvious that TS is not asking for string manipulation, isn't it? – hakre May 01 '12 at 12:58
OP asked for output of 3.00, AFAIK that's the only way to do it – Jeff Lambert May 01 '12 at 12:59
@watcher: Yes if you treat the input as a constant, yours ain't wrong, but [it's not the only way to do it, round works perfectly well](http://stackoverflow.com/a/10397974/367456). – hakre May 01 '12 at 13:03

score 2 · Answer 2 · answered May 01 '12 at 13:01

2

In case you are looking for the small fraction of your number being outputted in a formatted fashion:

$number = 3.0000000054978E+38;
printf('%.2f', $number / 1E+38); # 3.00

answered May 01 '12 at 13:01

hakre

I'm not really sure it's better in the eye of the TS, it's still undefined what Acubi is specifically looking for. – hakre May 01 '12 at 13:04

score 1 · Answer 3 · answered May 01 '12 at 12:46

1

You can just use round, as in round($floating_number, 2).

answered May 01 '12 at 12:46

Explosion Pills

Just out of interest, what's the advantage of this over number_format(3.0023123121, 2);? – SpaceBeers May 01 '12 at 12:47
`number_format` enforces the decimal places; actually it might be better to use in this case :P – Explosion Pills May 01 '12 at 12:48
Worth putting in the answers then. Ta. – SpaceBeers May 01 '12 at 12:50

score 1 · Answer 4 · answered May 01 '12 at 12:49

1

sprintf() always gives you the specified number of decimal points, if you require.

sprintf('%0.2f', 3.0000000);

Would display 3.00, if you echo it.

answered May 01 '12 at 12:49

Lion

4 Answers4