PHP File handling Convenience functions
Example
Raw direct IO
file_get_contents and file_put_contents provide the ability to read/write from/to a file to/from a PHP string in a single call.
file_put_contents can also be used with the FILE_APPEND bitmask flag to append to, instead of truncate and overwrite, the file. It can be used along with LOCK_EX bitmask to acquire an exclusive lock to the file while proceeding to writing. Bitmask flags can be joined with the | bitwise-OR operator.
$path = "file.txt";
// reads contents in file.txt to $contents
$contents = file_get_contents($path);
// let's change something... for example, convert the CRLF to LF!
$contents = str_replace("\r\n", "\n", $contents);
// now write it back to file.txt, replacing the original contents
file_put_contents($path, $contents);
FILE_APPEND is handy for appending to log files while LOCK_EX helps prevent race condition of file writing from multiple processes. For example, to write to a log file about the current session:
file_put_contents("logins.log", "{$_SESSION["username"]} logged in", FILE_APPEND | LOCK_EX);
CSV IO
fgetcsv($file, $length, $separator)
The fgetcsv parses line from open file checking for csv fields. It returns CSV fields in an array on success or FALSE on failure.
By default, it will read only one line of the CSV file.
$file = fopen("contacts.csv","r");
print_r(fgetcsv($file));
print_r(fgetcsv($file,5," "));
fclose($file);
contacts.csv
Kai Jim, Refsnes, Stavanger, Norway
Hege, Refsnes, Stavanger, Norway
Output:
Array
(
[0] => Kai Jim
[1] => Refsnes
[2] => Stavanger
[3] => Norway
)
Array
(
[0] => Hege,
)
Reading a file to stdout directly
readfile copies a file to the output buffer. readfile() will not present any memory issues, even when sending large files, on its own.
$file = 'monkey.gif';
if (file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.basename($file).'"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
readfile($file);
exit;
}
Or from a file pointer
Alternatively, to seek a point in the file to start copying to stdout, use fpassthru instead. In the following example, the last 1024 bytes are copied to stdout:
$fh = fopen("file.txt", "rb");
fseek($fh, -1024, SEEK_END);
fpassthru($fh);
Reading a file into an array
file returns the lines in the passed file in an array. Each element of the array corresponds to a line in the file, with the newline still attached.
print_r(file("test.txt"));
test.txt
Welcome to File handling
This is to test file handling
Output:
Array
(
[0] => Welcome to File handling
[1] => This is to test file handling
)
