写入文件时出现意外的PHP换行符

Question

I am trying to make a web based chat room and I am storing messages in a text file. But when writing to the file sometimes the line just breaks and starts a new one mid-string, my code for writing:

$_msg_file=fopen("message.txt","a");
stream_filter_append($_msg_file, 'convert.iconv.UTF-8/OLD-ENCODING');
///WRITE TO FILE
if($_SESSION["class"]==="admin")
{
    fwrite($_msg_file,"<li><b style='color:#FF9393;'>".$_SESSION["name"]."</b> ".$_POST["msg"]."</li>
");
}else {
    fwrite($_msg_file,"<li><b style='color:black;'>".$_SESSION["name"]."</b> ".$_POST["msg"]."</li>
");
}
fclose($_msg_file);

Output: http://pastebin.com/0cucqbTW

My jQuery for posting text:

var data={};
data["why"]="send";
data["msg"]=$(".box_msg").val();
if(data["msg"].length<100 && data["msg"].length>1)
{
$.ajax({
  type:"POST",
  url:"send.php",
  data:data,
  success:function(response)
  {
      $(".box_msg").val("");
  },
  error:function(response)
  {
      $("#chat").text(response);
  }
});

Answer 1

What you have is linebreak characters that you can't see but that are being sent within the $_POST value, as mentioned by Marc B.

The work around to this is to remove the PHP End of Line Characters, which are handily referenced as PHP_EOL.

(Personally I would also reference array keys in single quotes as double quotes effects quote references and such within the array values)

So

$_POST['msg'] = str_replace(PHP_EOL, '', $_POST['msg']);
// str_replace($search,replace,subject);

This will remove system used line breaks from the string, before you can then save to the file. You can additionally replace standard line break [type character]s such as and ( is not actually a linebreak as such, exactly) in case they're different from the PHP_EOL value :

Also suggested you save the changes as another variable rather than the original POSTed data.

$breaks = array("
","",PHP_EOL);
$strippedMessage = str_replace($breaks, '', $_POST['msg']);