How to capture serial data and show it in a php webpage?

If the monitoring is web based you can use Perl with module device:SerialPort or PHP with php_serial_class; there are other options to write what you need but using Perl or Php you can find many examples on web.
All "todo" is to read the data from serial port, split(Perl)/(explode Php) it using the pipe (|) char and print the resulting array rows (quite similar in both languages).
You might also use bash or Perl to write a simple text console monitor; in this case you don't need Apache