PHP: decimal format and mysql - php

Question

I have a form where the users write different numbers and can be decimal, but the format is different from the PHP and MySQL default format. This is the format I work with:
1,1 (one dot one) - 1.000,90 (one thousand and 90) - 1.000.000,90 (one million and 90), etc
Right now I have this function:
function formato_num($num){
$num = str_replace('.', '', $num);
$num = str_replace(',', '.', $num);
return $num;
}
It works fine in those cases but, if the user for some reason writes the decimal with a dot (.), it doesn't work.
I have this other function, but it doesn't work completely fine:
if(strpos($_POST['num'],'.') !== false){
$decimal = $_POST['num'];
$split = explode('.', $decimal);
$l = strlen($split[1]);
if($l < 3){
echo str_replace('.', ',', $_POST['num']);
}else{
$num = str_replace('.', '', $_POST['num']);
$num = str_replace(',', '.', $_POST['num']);
echo $num;
}
}
Any help? Thanks.
EXAMPLES:
If the user writes:
1.000 (one thousand) I save it on the DDBB as 1000.
1,2 (decimal) I save it as 1.1.
The problem is if the user use a dot for the thousand separator and decimal.

Answer 1

You can "easily" transform strings containing both: a comma and a dot, but especially if you want to support misplaced thousand-separators or allow the user to enter three decimal places ambiguities arise.
This is a best-effort approach which you could use. I while not be responsible for any misinterpreted numbers!
function stringToNumber($str) {
$last_comma = strrpos($str, ',');
$last_dot = strrpos($str, '.');
if($last_comma === false && $last_dot === false) {
return $str;
} elseif($last_comma !== false && $last_dot !== false) {
if($last_comma < $last_dot) {
// dot is further to the right
return str_replace(',', '', $str);
} else {
// comma is further to the right
return str_replace(',', '.', str_replace('.', '', $str));
}
} elseif ($last_dot !== false) {
// No commas. For thousand-separator the following must hold
if(preg_match('/^[0-9]{1,3}(\\.[0-9]{3})+$/', $str)) {
// every dot is followed by three digits... lets assume the user wanted them as thousand-separators
// For a single dot this assumption may be invalid, but we expect the user to use . as thousand-separator...
return str_replace('.', '', $str);
} else {
// We could check here how many dots are used.
return $str;
}
} else {
// No dots. For thousand-separator the following must hold
if(preg_match('/^[0-9]{1,3}(,[0-9]{3})+,[0-9]{3}$/', $str)) {
// every comma is followed by three digits and there are at least two of them
return str_replace(',', '', $str);
} else {
// So this is it. Single comma. We could check if the comma is followed by three digits, but it still could be legitimate and while we want to support unexpected input we do not want to interfere with valid input like "1,234" meant as 1.234
return str_replace(',', '.', $str);
}
}
}
Examples:
function formated_test($str) {
$num = stringToNumber($str);
printf("% 14s => % 14s\n", $str, $num);
}
formated_test("42");
formated_test("42.1");
formated_test("42,1");
formated_test("42.123");
formated_test("42,123");
formated_test("42.123,42");
formated_test("42,123.42");
formated_test("42.123.456");
formated_test("42,123,456");
formated_test("42.123.456,12");
formated_test("42,123,456.12");
And output:
42 => 42
42.1 => 42.1
42,1 => 42.1
42.123 => 42123
42,123 => 42.123
42.123,42 => 42123.42
42,123.42 => 42123.42
42.123.456 => 42123456
42,123,456 => 42123456
42.123.456,12 => 42123456.12
42,123,456.12 => 42123456.12