(PHP 4, PHP 5)
fseek — Seeks on a file pointer
$handle
, int $offset
[, int $whence
= SEEK_SET
] )
Sets the file position indicator for the file referenced by
handle
. The new position, measured in bytes
from the beginning of the file, is obtained by adding
offset
to the position specified by
whence
.
In general, it is allowed to seek past the end-of-file; if data is then written, reads in any unwritten region between the end-of-file and the sought position will yield bytes with value 0. However, certain streams may not support this behavior, especially when they have an underlying fixed size storage.
handle
A file system pointer resource that is typically created using fopen().
offset
The offset.
To move to a position before the end-of-file, you need to pass
a negative value in offset
and
set whence
to SEEK_END
.
whence
whence
values are:
SEEK_SET
- Set position equal to offset
bytes.SEEK_CUR
- Set position to current location plus offset
.SEEK_END
- Set position to end-of-file plus offset
.Upon success, returns 0; otherwise, returns -1.
Example #1 fseek() example
<?php
$fp = fopen('somefile.txt', 'r');
// read some data
$data = fgets($fp, 4096);
// move back to the beginning of the file
// same as rewind($fp);
fseek($fp, 0);
?>
Note:
If you have opened the file in append (a or a+) mode, any data you write to the file will always be appended, regardless of the file position, and the result of calling fseek() will be undefined.
Note:
Not all streams support seeking. For those that do not support seeking, forward seeking from the current position is accomplished by reading and discarding data; other forms of seeking will fail.