Converting long strings to decimals with more than 13 places

Question

This function is converting an array which may contain strings to numbers which may or may not have a decimal.

function toNumberArray(array $stringArray) {
    print_r ($stringArray);
    echo "<hr>";
    $n = [];
    for ($i = 0; $i < count($stringArray); $i++) {
        $n[] = settype ( $stringArray[$i],"float");
        $x = (float) $stringArray[$i];
        echo $x;
        echo "<br>";
    }
    return $n;
}

print_r (toNumberArray(["1.123456789012345","2.2000000000000002","3.2999999999999998"]));

Results:

Array ( [0] => 1.123456789012345 [1] => 2.2000000000000002 [2] => 3.2999999999999998 )

---

1.1234567890123

2.2

3.3

Array ( [0] => 1 [1] => 1 [2] => 1 )

Question:

Why is settype not converting the string to a float?

How to convert if there are 14 or more places after the decimal?

Answer 1

It is converting to a PHP float which is a 64-bit IEEE floating point number. You are probably expecting that PHP uses a 32-bit IEEE floating point number for float and a 64-bit IEEE floating point number for a double'. But, in PHPfloatanddouble` are synonyms. (see the link in jorgonor's comment).

You could use PHP's round function to convert the 64-bit number to 6 or 7 decimal points to simulate the effect you are probably looking for. See http://php.net/manual/en/function.round.php