如何使用多个正负符号将字符串转换为int？

Question

I'm trying to cast string to int. Everything work fine but have a small problem here

echo (int)"--12"; //return 0, i want 12
echo (int)"---23";//return 0, i want -23
echo (int)"+-99"; //return 0, i want -99
...

Why did this happened and what is the right way to cast in this case? Many thanks!

Answer 1

To evaluate the positive and negative signs so that all positive symbols are ignored and two negatives equal a positive, you can perform a replacement.

Code: (Demo)

$signed_number_strings = ["--1", "---33", "+-444"];

foreach ($signed_number_strings as $string) {
    var_dump((int)preg_replace('~\++|-\+*-\+*~', '', $string));
}

Output:

int(1)
int(-33)
int(-444)

The logic behind the pattern is to first match/remove 1 or more consecutive + signs, OR a - sign followed by zero or more + followed by a - (and absorbing any trailing + signs). If there are any fringe cases that my pattern doesn't correctly handle, please update your question and leave me a comment.

p.s. The extension of my 2nd branch with \+* is an attempt to optimize the pattern so that it doesn't have to restart the pattern. It could have been written as ~\++|-\+*-~ which would be slightly less strain on the eyeballs. (Demo)

Answer 2

you can extract number from string . can help?!

$str = '--1';
preg_match_all('!\d+!', $str, $matches);
print_r($matches);

Answer 3

I am not 100% sure on your use case but I knocked up this function to try and handle a string with numbers and to return the first full number with negative signed support.

I am sure I have your use case wrong but you can butcher this function however you like to drop the negative signed handling or to possibly handle floats where a decimal place may be needed for detection.

Worth noting that a regex may even exist for this.. who knows.

function intvaljunk($string) {
    $boolSignedNegative = false;
    $intIntStart = null;
    $intIntEnd = null;
    foreach (str_split($string) as $index => $char) {
        if (is_numeric($char)) {
            $boolSignedNegative = (
                $boolSignedNegative === false
                && $index > 0
                && is_null($intIntStart)
                && $string[$index - 1] === '-'
                    ? true
                    : $boolSignedNegative
            );
            $intIntStart = is_null($intIntStart) ? $index : $intIntStart;
            $intIntEnd = is_null($intIntStart) ? $intIntEnd : $index;
        } else if (!is_null($intIntStart) && !is_null($intIntStart)) {
            break;
        }
    }

    return (
        !is_null($intIntStart) && !is_null($intIntStart)
        ? intval(($boolSignedNegative ? '-' : '') . substr($string, $intIntStart, ($intIntEnd - $intIntStart) + 1))
        : null
    );
}

echo intvaljunk("--1") . PHP_EOL;
echo intvaljunk("---1") . PHP_EOL;
echo intvaljunk("+-1") . PHP_EOL;
echo intvaljunk("+-14991abc667") . PHP_EOL;