Question

I need a regex which can basically check for space, line break etc after string.

So conditions are,

1. Allow special characters ., _, -, + inside the string [e-mail], @hello_world, @helloworld, etc.
2. Discard anything including special characters where there is no alpha-numeric string after them i.e. @helloworld.<space>, @helloworld-<space>, @helloworld.?, etc. must be parsed as @helloworld

My existing RegEx is /@([A-Za-z0-9+_.-]+)/ which works perfectly Condition #1, but still there seems to be a problem Condition #2

I am using above RegEx in preg_replace()

Solution:

$str = preg_replace('#@[\w+.\-]+\b#', '[[$0]]', $str);

This works perfectly.

Tested with

http://gskinner.com/RegExr/

Answer 1

You can use word boundaries to easily find the position between an alphanumeric letter and a non-alphanumeric letter:

$str = preg_replace('#@[\w+.\-]+\b#', '[[$0]]', $str);

Working example: http://ideone.com/0ShCm