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?

Demo: https://regex101.com/r/x2W3S5/1

CodePudding user response：

Use a full string match restart (\K) instead of the invalid variable-length lookbehind.

Regex 101 Demo

(?:username|Email|Url):? *\K[^\v] 

Make the colon and space optional by trailing them with ? or *.

See also: Variable-length lookbehind-assertion alternatives for regular expressions

CodePudding user response：

Sadly, js does't have regexp lookbehide. This may help you solve this: javascript regex lookbehide alternative