php - 如何在PHP中用加号前缀正数

Question

我需要设计一个函数来原样返回负数，但如果它已经不存在，则应该在数字的开头添加一个 + 符号。

例子:

Input     Output
----------------
+1         +1
1          +1
-1         -1

它将只获得数字输入。

function formatNum($num)
{
# something here..perhaps a regex?
}

这个函数会在echo/print中被调用多次，所以越快越好。

Answer 1

您可以将正则表达式用作:

function formatNum($num){
    return preg_replace('/^(\d+)$/',"+$1",$num);
}

但我建议 不要 使用 regex 来处理这种微不足道的事情。最好使用sprintf这里是:

function formatNum($num){
    return sprintf("%+d",$num);
}

来自 PHP Manual for sprintf :

An optional sign specifier that forces a sign (- or +) to be used on a number. By default, only the - sign is used on a number if it's negative. This specifier forces positive numbers to have the + sign attached as well, and was added in PHP 4.3.0.