'Regex Error: A lookbehind assertion has to be fixed width [duplicate]
My pattern works in JavaScript.
(?<=(?:username|Email|URL)(?:\s|:))[^\n]+
However, when I try to use it in PHP, I get this error:
A lookbehind assertion has to be fixed width
How I can fix it?
Solution 1:[1]
Use a full string match restart (\K) instead of the invalid variable-length lookbehind.
/^(?:username|Email|Url):? *\K\V+/mi
Make the colon and space optional by trailing them with ? or *.
Use \V+ to match the remaining non-vertical (such as \r and \n) characters excluding in the line.
See the broader canonical: Variable-length lookbehind-assertion alternatives for regular expressions
To protect your script from falsely matching values instead of matching labels, notice the use ^ with the m modifier. This will ensure that you are matching labels that occur at the start of a line.
Without a start of line anchor, Somethingelse: url whoops will match whoops.
To make multiple matches in PHP, the g pattern modifier is not used. Instead, apply the pattern in preg_match_all()
Solution 2:[2]
Sadly, js does't have regexp lookbehide. This may help you solve this: javascript regex lookbehide alternative
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
| Solution | Source |
|---|---|
| Solution 1 | |
| Solution 2 | M.Smith |