正则表达式查找后面

Question

我想是的后面是一个关键的词“量”

preg_match_all("/amount.+\b(\d+(\.\d+)?)/im", $input_lines, $output_array);

我输入的数据是

here is some number 100.25 
that does not 200. 
but this amount should be captured 300. 
and this amount should be captured 400.25 too 
and this amount should be captured $5023 too 
and this amount should be captured $60.25 too 
and this amount should be captured 700.25. 

But not this amount 800.25.2 

文本中捕捉数量的关键词数量

所以只有数字300，400.25，5023，60.25，700.25应该被捕获

Answer 1

你正在寻找的正则表达式是：amount\D+(\d+(?:\.\d+)?)\.?(?!\d)

看到它在这里的行动：https://regex101.com/r/iXwM40/1

这依赖于有是单词“量”和组数字之间没有号码。

这个关键是最后一组括号，它被称为负向预览：(?!\d)如果下面的字符是数字位，这将不匹配。 \d

查看向前看符号这里更多的信息：http://www.regular-expressions.info/lookaround.html

Answer 2

用下面的办法：

$input_lines = "here is some number 100.25 
that does not 200. 
but this amount should be captured 300. 
and this amount should be captured 400.25 too 
and this amount should be captured $5023 too 
and this amount should be captured $60.25 too 
and this amount should be captured 700.25. 

But not this amount 800.25.2"; 

preg_match_all("/(?:amount [^\d]+?)\K\d+(\.\d+)?/m", $input_lines, $matches); 

print_r($matches[0]); 

输出： 阵列

(
    [0] => 300 
    [1] => 400.25 
    [2] => 5023 
    [3] => 60.25 
    [4] => 700.25 
) 

---

(?:amount [^\d]+?) - 匹配字符串（线）与amount后跟除数字以外的任何字符

\K - 重置报告的匹配的起点。任何先前消耗的字符都不再包含在最终的比赛

\d+(\.\d+)? - 所需要的数量（包括如果它是浮动的小数部分）

Answer 3

给匹配这样的尝试\bamount\b.*?(\d+(?:\.\d*)?|\.\d+)

\b amount \b .*? 
(       # (1 start) 
     \d+ 
     (?: \. \d*)? 
    | \. \d+ 
)        # (1 end)