str_replace help

["David Stoltz" <Dstoltz@xxxxxxx>]

Hi folks,
 
In ASP, I would commonly replace string line feeds for HTML output like
this:
 
Var = replace(value,vbcrlf,"<br>")
 
In PHP, the following doesn't seem to work:
$var = str_replace(chr(13),"\n",$value)
 
Neither does:
$var = str_replace(chr(10),"\n",$value)
 
What am I doing wrong?
 
Thanks!