nl2br not working for me

I know this is an old post but if like me you are have stumbled across this issue and the above didn't work for you, this solution may help you instead:

echo nl2br(stripslashes($row["comments"]));

or (they are not the same function, note the additional "c" after strip)

echo nl2br(stripcslashes($row["comments"]));

See original thread that helped me: nl2br() not working when displaying SQL results

try this:

echo preg_replace('/\v+|\\\r\\\n/Ui','<br/>',$row["comments"]);

Most likely you are doing escaping twice, when adding your data into DB.
Check your code that adds data to DB and remove unnecessary escaping.

Most likely it's some senseless "universal sanitization" function.

Well it's easy.
Let's take a quote, not a newline to demonstrate. The behavior the same. Slashes being stripped then data goes to database.

Thus, in the normal case:

source: It's
after escaping: It\'s
by the query execution slash being stripped and
both in the database and back It's

in double escaping case:

source: It's
after escaping: It\'s
after second escaping: It\\\'s
by the query execution slash being stripped and
both in the database and back It\'s
we have our data spoiled.

Just make yourself understand that escaping i not something magical that makes your data "safe" (and, therefore can be done many times, as you probably think). It's just adding a backslash to certain symbols.