PHP - How to set regex boundary and not match non alphanumeric char?

问题

Consider the following:

$text = 'c c++ c# and other text'; 
$skills = array('c','c++','c#','java',...);

foreach ($skill as $skill) {
    if (preg_match('/\b'.$skill.'\b/', $text)) {
        echo $skill.' is matched';
    }
}

In the case of 'c', it matches 'c', 'c#', and 'c++'. I've tried appending assertion (?=\s) or [\s|.] in place of \b towards the end but it needs something similar to \b.

I've checked out other posts but doesn't seem to have the exact situation. Thanks!

回答1:

The problem is that \b matches between c and + or #. You need something like this:

$text = 'c c++ c# and other text'; 
$skills = array('c','c++','c#','java');

foreach ($skills as $skill) {
    if (preg_match('/(?<=^|\s)'.preg_quote($skill).'(?:\s|$)/', $text)) {
        echo $skill.' is matched';
    }
}

This matches when the text is preceded by either the start of the string (^) or a space at the beginning, and followed by either the end of the string ($) or a space at the end.

You need to use preg_quote(), like I did above, because c++ contains regex special characters.

Also, note the typo (missing s) in foreach ($skills ... ) in your original code.

回答2:

Part of the problem is that c++ has regex chars in it. You should use preg_quote on $skill. Then use your back and forward reference solution.

The other issue is that you need to double escape the special characters because php also uses \ as an escape character in strings.

来源：https://stackoverflow.com/questions/20560303/php-how-to-set-regex-boundary-and-not-match-non-alphanumeric-char