正則表達式查找後面

Question

我想是的後面是一個關鍵的詞「量」

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

我輸入的數據是

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 

文本中捕捉數量的關鍵詞數量

所以只有數字300，400.25，5023，60.25，700.25應該被捕獲

Answer 1

你正在尋找的正則表達式是：amount\D+(\d+(?:\.\d+)?)\.?(?!\d)

看到它在這裏的行動：https://regex101.com/r/iXwM40/1

這依賴於有是單詞「量」和組數字之間沒有號碼。

這個關鍵是最後一組括號，它被稱爲負向預覽：(?!\d)如果下面的字符是數字位，這將不匹配。 \d

查看向前看符號這裏更多的信息：http://www.regular-expressions.info/lookaround.html

Answer 2

用下面的辦法：

$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]); 

輸出： 陣列

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

---

(?:amount [^\d]+?) - 匹配字符串（線）與amount後跟除數字以外的任何字符

\K - 重置報告的匹配的起點。任何先前消耗的字符都不再包含在最終的比賽

\d+(\.\d+)? - 所需要的數量（包括如果它是浮動的小數部分）

Answer 3

給匹配這樣的嘗試\bamount\b.*?(\d+(?:\.\d*)?|\.\d+)

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