php 如何在PHP中用加号前缀一个正数
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How to prefix a positive number with plus sign in PHP
提问by user318466
I need to design a function to return negative numbers unchanged but should add a +sign at the start of the number if its already no present.
我需要设计一个函数来返回负数不变但应该+在数字的开头添加一个符号，如果它已经不存在。
Example:
例子：
Input Output
----------------
+1 +1
1 +1
-1 -1
It will get only numeric input.
它只会得到数字输入。
function formatNum($num)
{
# something here..perhaps a regex?
}
This function is going to be called several times in echo/printso the quicker the better.
这个函数会被多次调用，echo/print所以越快越好。
Update:
更新：
Thank you all for the answers. I must tell the sprintfbased solution is really fast.
谢谢大家的回答。我必须告诉sprintf基于的解决方案真的很快。
回答by codaddict
You can use regex as:
您可以将正则表达式用作：
function formatNum($num){
return preg_replace('/^(\d+)$/',"+",$num);
}
But I would suggest notusing regexfor such a trivial thing. Its better to make use of sprintfhere as:
但我建议不要使用regex这种微不足道的东西。最好在这里使用sprintf作为：
function formatNum($num){
return sprintf("%+d",$num);
}
From 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 attachedas well, and was added in PHP 4.3.0.
强制在数字上使用符号（- 或 +）的可选符号说明符。默认情况下，如果数字是负数，则仅在数字上使用 - 符号。此说明符强制正数也附加 + 号，并在 PHP 4.3.0 中添加。
回答by Dal Hundal
function formatNum($num) {
return ($num>0)?'+'.$num:$num;
}
回答by pinkgothic
function formatNum($num) {
$num = (int) $num; // or (float) if you'd rather
return (($num >= 0) ? '+' : '') . $num; // implicit cast back to string
}
回答by rancho
The simple solution is to make use of format specifier in printf() function.
简单的解决方案是在 printf() 函数中使用格式说明符。
For example,
例如，
$num1=2;
$num2=-2;
printf("%+d",$num1);
echo '<br>';
printf("%+d",$num2);
gives the output
给出输出
+2
-2
In your case
在你的情况下
function formatNum($num){
return printf("%+d",$num);
}
回答by nikc.org
The sprintfsolution provided by @unicornaddict is very nice and probably the most elegant way to go. Just thought I'd provide an alternative anyway. Not sure how they measure up in speed.
sprintf@unicornaddict 提供的解决方案非常好，可能是最优雅的方式。只是想无论如何我都会提供替代方案。不确定他们如何衡量速度。
// Non float safe version
function formatNum($num) {
return (abs($num) == $num ? '+' : '') . intval($num);
}
// Float safe version
function formatNum($num) {
return
(abs($num) == $num ? '+' : '')
. (intval($num) == $num ? intval($num) : floatval($num));
}
// Float safe version, alternative
function formatNum($num) {
return
(abs($num) == $num ? '+' : '')
// Add '1' to $num to implicitly cast it to a number
. (is_float($num + 1) ? floatval($num) : intval($num));
}
