Convert a String Containing a Number in Scientific Notation to a Double in PHP

Convert a string containing a number in scientific notation to a double in PHP

PHP is typeless dynamically typed, meaning it has to parse values to determine their types (recent versions of PHP have type declarations).

In your case, you may simply perform a numerical operation to force PHP to consider the values as numbers (and it understands the scientific notation x.yE-z).

Try for instance

  foreach (array("1.8281e-009","2.3562e-007","0.911348") as $a)
  {
    echo "String $a: Number: " . ($a + 1) . "\n";
  }

just adding 1 (you could also subtract zero) will make the strings become numbers, with the right amount of decimals.

Result:

  String 1.8281e-009: Number: 1.0000000018281
  String 2.3562e-007: Number: 1.00000023562
  String 0.911348:    Number: 1.911348

You might also cast the result using (float)

  $real = (float) "3.141592e-007";

convert a scientific notation/exponential number

You can use the number_format() function; e.g.

<?php
$awb = "4.96e-6";
print number_format($awb, 10);
?>

Will result in the output: 0.0000049600.

See: http://php.net/manual/en/function.number-format.php

PHP how to convert number exponential number to string?

printf and friends will do this:

<?php
$awb = 2.01421700079E+14;
$str = sprintf("%d", $awb);
var_dump($str);

Output:

string(15) "201421700079000"

There obviously isn't enough information in your original number to get any more precision than that.

scientific notation to normal decimal output conversion

I found a way to do it myself and I am posting a quick answer.

function realval($v) {
    $f = (string)number_format($v, 10, '.', ''); // 10000.0000010000
    if(strpos($f, '.') !== false) { // if it's a decimal (if not, print as is)
        $f = rtrim($f, "0"); // 10000.000001
        $f = rtrim($f, "."); // to prevent 10000. like things. 
    }
    return $f; // string format
}

This does what I needed. I wanted a more decent way to do so, but not figured out yet.

incorrect number from scientific notation in PHP

Note that the double floating point format has a precision of about 15.5 decimals. All other displayed decimals are extrapolated. And as always, extrapolation is a dangerous game.

Or in other words, 3.2486509223274E+19 represents an interval, roughly from 3.24865092232739984E+19 to 3.24865092232740024E+19. Any integer in that interval has to count as "correct" extrapolation.

BC math string into scientific notation

Count how many zeroes there are.

Note that because you are using big numbers, you have to work on them as strings. So...

if( preg_match("/^0\.0*/",$value,$m)) {
    $zeroes = strlen($m[0]);
    $value = substr($value,$zeroes,1)
                .rtrim(".".substr($value,$zeroes+1),"0.")
                ."E-".($zeroes-1);
}
elseif( preg_match("/(\d+)(?:\.(\d+))?/",$value,$m)) {
    $zeroes = strlen($m[1]);
    $value = substr($value,0,1)
                .rtrim(".".substr($m[1],1).$m[2],"0.")
                ."E+".($zeroes-1);
}
// else 1 <= number < 10, so no transformation needed

Test cases:

• 1000000 => 1E+6
• 1234.5678 => 1.2345678E+3
• 0.9 => 9E-1
• 0.123 => 1.23E-1
• 0.00000011111122222 => 1.1111122222E-7

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