PHP编号：将1.4EN（N> 40）转换为十进制，删除无用的零位数

Question

I am getting very small values from a third party service, I need it to convert to number with useless digits removed. `

<?php 
    $decimal = 50 
    //If value is 1.4E-45
    number_format($value, $decimal); 
    //output: 0.00000000000000000000000000000000000000000000140000 
    number_format($value, $decimal) +0 ;
    //output: 1.4E-45 
?>

`

Sample Input ::

• 1

  output 1

• 1.00000000000000000000000000000000000000000000000000

  output : 1

• 1.4E-45

  output : 0.0000000000000000000000000000000000000000000014

As you can see in code, already tried out to add 0 and number_format method.

There can be two approaches

1. found out $decimal value need to be used dynamically
2. Always pass maximum possible value of $decimal and remove useless 0. We can assume an upper limit of $decimal as 50.

Please suggest if any method in php function available for any of the approach

Answer 1

I'd recommend this approach:

<?php


function getRidOfExtraZeros($str)
{
    // Don't want to rtrim whole numbers
    if(strpos($str,'.') === false ){ return $str; }

    // Don't want to rtrim scientific notation
    if(stripos($str,'e') !== false ){ return $str; }

    // We're good to go
    return rtrim(rtrim($str, '0'),'.');
}

$value = '0.00000000000000000000000000000000000000000000140000';

echo getRidOfExtraZeros($value),"\n"; // 0.0000000000000000000000000000000000000000000014
echo getRidOfExtraZeros('30'),"\n"; // 30
echo getRidOfExtraZeros('30.79e10'),"\n"; // 30.79e10
echo getRidOfExtraZeros('0.0'),"\n"; // 0
echo getRidOfExtraZeros('0.'),"\n"; // 0

Alternatively cast your string to float if you don't mind precision loss in edge cases and seeing some scientific notation. A carefully used rtrim is probably the best approach.

Answer 2

You set the decimals to 50, that is why it outputs the last zeros.
If you calculate what $decimals should be then it should give you what you need.

$value = 0.0000000000000000000000000000000000000000000014;
// Find what the number is 
$end = str_replace(".", "", explode("E-", $value)[0]); // 14
// Find consecutive zeros to $end
Preg_match("/\.\d+" . $end ."/", number_format($value, 100), $match);
$decimal = strlen($match[0])-1; // make that number the end -1 due to the dot

Echo number_format($value, $decimal);

https://3v4l.org/fE1XD

It ain't pretty but it works for this.

Edit: I have numberformat ($value, 100 ) because I need to be sure to get the full number as a float value.
Then I use the preg_match to find the pattern [0] and what your number is on this float number.

Edit 2. This will show you why a fixed decimals is not a good solution.
Floating numbers are not precise.
https://3v4l.org/Ai0kE