I'm sure it's way over 64k, having used it for things larger than that in the past, but it is SLOW to use, especially if you want each line split out. If that's what you want, then use fgets like so:
<?php
$filename = "myfile.txt";
$fp = fopen($filename,"r");
while (!feof($fp)){
$line=fgets($fp,4096);
$d = split(" *| *",$line);
$data[]=$d;
}
?>
That will build you a two D array where the first index is the record index and the scond the field index.
Generally, for reading text and ripping it into arrays, freading and splitting the whole thing twice are kinda slow compared to fgets and one split per line.