(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
Wskaźnik do systemu plików typu resource jest zazwyczaj tworzony poprzez funkcję 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.
Przykład #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);
?>
Informacja:
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.
Informacja:
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.