regexp monetary strings with decimals and thousands separator

Question

https://www.tehplayground.com/KWmxySzbC9VoDvP9

Why is the first string matched?

$list = [
    '3928.3939392',     //  Should not be matched
    '4.239,99',
    '39',
    '3929',
    '2993.39',
    '393993.999'
];

foreach($list as $str){
    preg_match('/^(?<![\d.,])-?\d{1,3}(?:[,. ]?\d{3})*(?:[^.,%]|[.,]\d{1,2})-?(?![\d.,%]|(?: %))$/', $str, $matches);
    print_r($matches);
}

output

Array
(
    [0] => 3928.3939392
)
Array
(
    [0] => 4.239,99
)
Array
(
    [0] => 39
)
Array
(
    [0] => 3929
)
Array
(
    [0] => 2993.39
)
Array
(
)

For a detailed explanation of your current regex: regex101.com/r/ZoLUFf/1 — Jorge Campos
– Jorge Campos, Commented Dec 13, 2017 at 20:32
The (?<![\d.,]) is redundant as it always returns true: there can be no text before the start of the string. Try just ^-?(?:\d{1,3}(?:[,. ]\d{3})*|\d+)(?:[.,]\d{1,2})?$. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 13, 2017 at 20:32

Wiktor Stribiżew · Accepted Answer · 2017-12-13 20:47:36Z

2

You seem to want to match the numbers as standalone strings, and thus, you do not need the lookarounds, you only need to use anchors.

You may use

^-?(?:\d{1,3}(?:[,. ]\d{3})*|\d*)(?:[.,]\d{1,2})?$

See the regex demo

Details

^ - start of string
-? - an optional -
(?: - start of a non-capturing alternation group:
- \d{1,3}(?:[,. ]\d{3})* - 1 to 3 digits, followed with 0+ sequences of ,, . or space and then 3 digits
- | - or
- \d* - 0+ digits
) - end of the group
(?:[.,]\d{1,2})? - an optional sequence of . or , followed with 1 or 2 digits
$ - end of string.

answered Dec 13, 2017 at 20:47

Wiktor Stribiżew

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