Recipe 18.10 Processing a File Backward by Line or Paragraph
18.10.1 Problem
You want to do something
with each line of a file, starting at the end. For example,
it's easy to add new guestbook entries to the end of
a file by opening in append mode, but you want to display the entries
with the most recent first, so you need to process the file starting
at the end.
18.10.2 Solution
If the file fits in memory, use
file( ) to read each line in the file into an array
and then reverse the array:
$lines = file('guestbook.txt');
$lines = array_reverse($lines);
18.10.3 Discussion
You can
also iterate through an unreversed array of lines starting at the
end. Here's how to print out the last 10 lines in a
file, last line first:
$lines = file('guestbook.txt');
for ($i = 0, $j = count($lines); $i <= 10; $i++) {
print $lines[$j - $i];
}
18.10.4 See Also
Documentation on file( ) at
http://www.php.net/file and
array_reverse( ) at
http://www.php.net/array-reverse.
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