In the case of / \ b @ MYVAR \ b / i, I can not use boundary, See: link I need to validate a string that contains a @MYVAR (Example) word.
Are there any restrictions on this character? What would be an alternative?
I tested javascript and the result is false.
console.log('/\b@MYVAR\b/i.test("@MYVAR")',/\b@MYVAR\b/i.test("@MYVAR"));In php the code would look something like this:
<?php
$value = "@MYVAR";
if(preg_match("#/\b@MYVAR\b/i#i", trim($value))){
echo "ok";
}
The boundary ( \b ) applies only to letters, numbers, and the underline that would be the equivalent of \w ( [a-zA-Z0-9_] ) so its regex fails.
In this case you would have to leave the arroyo outside the boundary. Something like @\buserid\b or @?\buserid\b
The problem is that @ is not considered a valid character for word . That is, \b refers to the beginning of a word but the valid characters for \w are [a-zA-Z0-9_] , and @ is not there.
Complementing the concept:
The \b does not make selection. It is a anchor as well as ^ and $ and positions the cursor to positions that are between: (^\w|\w$|\W\w|\w\W) . In other words:
A char word is what is in [a-zA-Z0-9_] , that is, letters, digits, and underlines.
For example: said "i'm looking @ you" , \b would position (I'll mark with | ):
|i|'|m| |looking| @ |you|
I think these considerations may be helpful to some.
As quoted by the elder rray and Sergio , a word boundary is defined by starting with [a-z A-Z 1-9] characters, however this can be reversed with a regex like this: / p>
(@\buserid\b)
Explanation:
This regex identifies the @ character and only the match if there is the word "userid".