正则表达式模式与PHP匹配

Question

I have the following data in a file, which is repeated multiple times:

Date:21 Month:03 Year:2017 Amount:50 Category:Grocery Account:bank Note:expensive

Now, I want to extract the value after "Amount:", ie "50".

I'm using the following code in PHP:

$result = preg_split("/Amount/", $contents);
$truncated = substr($printresult, 1, 2);
print_r($truncated);

The result I'm getting is this:

    Da50

Could you please help me figure out what exactly I'm doing wrong in this code?

Thank you.

[Edit: $contents contains all the string data]

This is the entire code: http://paste.ideaslabs.com/show/hwj7IiPUcd Content of data.txt is this: http://paste.ideaslabs.com/show/5TxWH8MUX

Answer 1

you can try this

    $subject = "Date:21 Month:03 Year:2017 Amount:50 Category:Grocery Account:bank Note:expensive";

$pattern = "/Account/";

    preg_match($pattern, $subject, $matches);
    print_r($matches);

Answer 2

The da comes from the Date at the start of your string. You need to use preg_match or preg_match_all to extract exact matches. preg_split splits on the found term, index 0 you don't care about. Try:

$arraynext = 'Date:21
Month:03
Year:2017
Amount:50
Category:Wow
Account:The
Note:This';
$endresult = preg_match("/\s*Amount:\s*(\d+)/", $arraynext, $match);
echo $match[1];

Regex demo: https://regex101.com/r/SA48sm/1/

PHP Demo: https://3v4l.org/6jaCV

Answer 3

If you say that you have many coincidences, then you need to select all

preg_match_all('/(?<=Amount:)[\d]{0,}/', $contents, $result);
foreach($result as $res) {
    print_r($res);
}

Answer 4

You can use the following regex pattern ...

(?<=Amount:)\d+

see regex demo

PHP ( demo )

$regex = '/(?<=Amount:)\d+/';
$arraynext = file_get_contents('data.txt');
preg_match_all($regex, $arraynext, $result);
print_r($result);

Answer 5

Use this pattern: /Amount:\\K\\d+/
It will accurately extract the full desired numeric value that follows each Amount: without using the much less efficient "lookarounds".

My web filter software does not let me visit your pastelabs links, so I cannot see your actual input. (This is one of many reasons why you should post your input samples directly into your question.) You state that you have several lines which you must extract from, so this is the sample input that I have tested with:

Date:21 Month:03 Year:2017 Amount:50 Category:Grocery Account:bank Note:expensive
Date:1 Month:04 Year:2017 Amount:150 Category:Grocery Account:bank Note:expensive
Date:14 Month:04 Year:2017 Amount:5 Category:Grocery Account:bank Note:expensive
Date:28 Month:04 Year:2017 Amount:5935 Category:Grocery Account:bank Note:expensive

My pattern captures the desired results in just 48 steps . ( Pattern Demo )
The pattern uses \\K which means "KEEP the character starting from this point", so there is no need for a capture group, nor a "lookbehind".
If your actual input data has optional spaces between Amount: and the number value, then just add ? (space then question mark) to the pattern after the : .

When used with preg_match_all() , the output array is as small as preg_match_all() can make: an array containing 1 subarray with 4 elements. I cut directly to the subarray in my code to follow:

Code: ( Demo )

$in='Date:21 Month:03 Year:2017 Amount:50 Category:Grocery Account:bank Note:expensive
Date:1 Month:04 Year:2017 Amount:150 Category:Grocery Account:bank Note:expensive
Date:14 Month:04 Year:2017 Amount:5 Category:Grocery Account:bank Note:expensive
Date:28 Month:04 Year:2017 Amount:5935 Category:Grocery Account:bank Note:expensive';

var_export(preg_match_all('/Amount:\K\d+/',$in,$out)?$out[0]:[]);

Output:

array (
  0 => '50',
  1 => '150',
  2 => '5',
  3 => '5935',
)

---

As far as the other answers on this page, they all process my test data in over 600 steps (more than 12x slower / less efficient than my pattern). At the time of this post, one of them is completely wrong, and some use sloppy regex syntax and shouldn't be learned from.