[pdo_firebird] float, double value is incorrect

[SakiTakamachi]

Description

The following code:

<?php

$db = new PDO(/* firebird */);

$db->exec('CREATE TABLE test (f_val FLOAT, d_val DOUBLE PRECISION)');
$db->exec('INSERT INTO test VALUES (0.0000001, 0.00000001)');
$stmt = $db->query('select * from test');
var_dump($stmt->fetchAll(PDO::FETCH_ASSOC));

Resulted in this output:

array(1) {
  [0]=>
  array(2) {
    ["F_VAL"]=>
    string(8) "0.000000"
    ["D_VAL"]=>
    string(8) "0.000000"
  }
}

But I expected this output instead:

array(1) {
  [0]=>
  array(2) {
    ["F_VAL"]=>
    string(8) "0.0000001"
    ["D_VAL"]=>
    string(8) "0.00000001"
  }
}

After trying various things, it seems that the fraction part is displayed as a fixed 6 digits. e.g. 12.000000001 => 12.000000
It's late today, so I'll try again tomorrow.

(In the first place, I think I want the value to be a native type, but I won't consider that for now.)

PHP Version

= PHP8.2

Operating System

Ubuntu20.04(docker)

[SakiTakamachi]

ZVAL_STR(result, zend_strpprintf(0, "%F", php_get_double_from_sqldata(var->sqldata)));

{gc = {refcount = 1, u = {type_info = 22}}, h = 0, len = 8, val = "0"}

php_get_double_from_sqldata is fine, so maybe there's something with zend...

[SakiTakamachi]

Since the process was similar to sprintf, I referred to the documentation.

https://www.php.net/manual/en/function.sprintf.php#refsect1-function.sprintf-parameters

For e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6).

It was by design, not a bug in zend. However, this specification is inappropriate for obtaining fetched values, so I should consider other methods.

[SakiTakamachi]

@nielsdos
It seems to start using zend_strpprintf after #10920, is there any reason why the fraction part has a fixed number of digits?

If there is no particular reason, I think it would be better to use zend_gcvt.
(Indeed, zend_gcvt is used to convert float to double in mysqlnd)

[SakiTakamachi]

TBH, it may be simpler to make it a native type.

However, since changing the type is a BC break, it may be a good idea to leave 8.2 and 8.3 as string type, and make master a native type.

[nielsdos]

@SakiTakamachi the zend_strpprintf function was already used prior to my PR.
But I agree that zend_gcvt is probably right, and that on master native types would be preferable (but would at the very least require a mail to the ML due to BC break)

[SakiTakamachi]

@nielsdos
Oops, I'm very sorry! I missreaded that.
Thank you for checking.

[SakiTakamachi]

BTW, strangely, firebird's float type can be saved as is in the DB even with a number of digits like 12.345678.