PHP Cookbook

18.15. Removing the Last Line of a File

Problem

You want to remove the last line of a file; for example, someone’s added a comment to the end of your guestbook. You don’t like it, so you want to get rid of it.

Solution

If the file is small, you can read it into an array with file( ) and then remove the last element of the array:

$lines = file('employees.txt');
array_pop($lines);
$file = join('',$lines);

Discussion

If the file is large, reading it into an array requires too much memory. Instead, use this code, which seeks to the end of the file and works backwards, stopping when it finds a newline:

$fh = fopen('employees.txt','r') or die("can't open: $php_errormsg"); $linebreak = $beginning_of_file = 0; $gap = 80; $filesize = filesize('employees.txt'); fseek($fh,0,SEEK_END); while (! ($linebreak || $beginning_of_file)) { // save where we are in the file $pos = ftell($fh); /* move back $gap chars, use rewind() to go to the beginning if * we're less than $gap characters into the file */ if ($pos < $gap) { rewind($fh); } else { fseek($fh,-$gap,SEEK_CUR); } // read the $gap chars we just seeked back over $s = fread($fh,$gap) or die($php_errormsg); /* if we read to the end of the file, remove the last character * since if it's a newline, we should ignore it */ if ($pos + $gap >= $filesize) { $s = substr_replace($s,'',-1); } // move back to where we were before we read $gap chars into $s if ($pos < $gap) { rewind($fh); } else { fseek($fh,-$gap,SEEK_CUR); } // is there a linebreak in ...