PHP fopen(): Open, Read and Write Files (Modes Explained)

fopen('data.txt', 'r') opens a file and returns a handle, a stream resource that the other file functions take as their first argument. Read with fgets() (one line) or fread() (a number of bytes), write with fwrite(), and close with fclose(). The second argument is the mode: 'r' to read, 'w' to write, 'a' to append.

<?php
$fh = fopen('fruits.txt', 'w');          // create or empty the file
fwrite($fh, "apple\n");
fwrite($fh, "banana\n");
fwrite($fh, "cherry\n");
fclose($fh);

$fh = fopen('fruits.txt', 'r');
if ($fh === false) {
    exit("Cannot open fruits.txt\n");
}

while (($line = fgets($fh)) !== false) {
    echo 'Got: ', rtrim($line), "\n";
}
fclose($fh);

Output:

Got: apple
Got: banana
Got: cherry

fopen() returns false when it cannot open the file (it does not exist in r mode, a folder is missing, no permission), and PHP prints a warning such as:

Warning: fopen(missing.txt): Failed to open stream: No such file or directory in /home/index.php on line 2

So check for false before using the handle. For reading or writing a whole small file in one call, file_get_contents() and file_put_contents() are shorter; fopen() is for files you read piece by piece or keep open.

fopen modes

Two rows surprise people. r+ writes over the existing bytes in place, without inserting, and a+ always writes at the end, even after you move the pointer with fseek() (moving it only affects reads):

<?php
file_put_contents('letters.txt', "abc\n");

$fh = fopen('letters.txt', 'r+');
fwrite($fh, 'X');                  // overwrites the "a"
fclose($fh);
echo file_get_contents('letters.txt');

$fh = fopen('letters.txt', 'a+');
fseek($fh, 0);                     // back to the start...
fwrite($fh, "end\n");              // ...but the write still goes to the end
rewind($fh);
echo fgets($fh);                   // reads do start at the beginning
fclose($fh);
echo file_get_contents('letters.txt');

Output:

Xbc
Xbc
Xbc
end

On Windows you may see 'rb' or 'wb': the b flag means binary and stops Windows from translating line endings. It does nothing on Linux and macOS, so adding it is harmless and portable.

Read a file line by line with fgets()

fgets() returns the next line including its \n, and false at the end of the file. Because only one line is in memory at a time, this loop handles a log file of any size, and you can stop early with break:

<?php
file_put_contents('app.log', <<<LOG
2026-03-14 09:00:01 INFO  server started
2026-03-14 09:00:05 ERROR database timeout
2026-03-14 09:01:12 INFO  request /home
2026-03-14 09:02:40 ERROR disk full
2026-03-14 09:03:00 INFO  request /about
LOG);

$fh = fopen('app.log', 'r');
$number = 0;
$errors = [];

while (($line = fgets($fh)) !== false) {
    $number++;
    if (str_contains($line, 'ERROR')) {
        $errors[] = "line $number: " . trim(substr($line, 26));
    }
}
fclose($fh);

echo count($errors), " errors in $number lines\n";
echo implode("\n", $errors), "\n";

Output:

2 errors in 5 lines
line 2: database timeout
line 4: disk full

Compare with false using !==, not with a plain while ($line = fgets($fh)): a line containing only "0" with no newline (the last line of a file can be one) is falsy and would end the loop early.

Write and append with fwrite()

fwrite() writes a string at the current position and returns the number of bytes written, or false on failure. fputs() is the same function under another name. Open with 'a' to add to the end of a file without touching what is there:

<?php
$fh = fopen('visits.log', 'a');
foreach (['/home', '/about', '/contact'] as $page) {
    $bytes = fwrite($fh, "visit $page" . PHP_EOL);
    echo "wrote $bytes bytes\n";
}
fclose($fh);

$fh = fopen('visits.log', 'a');      // open again: the old lines stay
fwrite($fh, 'visit /home' . PHP_EOL);
fclose($fh);

echo file_get_contents('visits.log');

Output:

wrote 12 bytes
wrote 13 bytes
wrote 15 bytes
visit /home
visit /about
visit /contact
visit /home

PHP_EOL is the line ending of the system PHP runs on (\n on Linux and macOS, \r\n on Windows). For files other programs read, pick one explicitly, usually "\n".

Read and write CSV files with fgetcsv() and fputcsv()

fputcsv() writes an array as one CSV row and quotes fields that contain commas, quotes or newlines. fgetcsv() reads one row back as an array. Pass the separator, the enclosure and an empty escape character explicitly: that gives standard CSV, and PHP 8.4 prints a deprecation notice when the escape argument is left out.

<?php
$rows = [
    ['name', 'city', 'note'],
    ['Ada', 'London', 'likes "math", a lot'],
    ['Linus', 'Helsinki', 'kernel'],
];

$fh = fopen('people.csv', 'w');
foreach ($rows as $row) {
    fputcsv($fh, $row, ',', '"', '');
}
fclose($fh);
echo file_get_contents('people.csv'), "\n";

// Read it back, using the first row as keys
$fh = fopen('people.csv', 'r');
$header = fgetcsv($fh, null, ',', '"', '');
while (($fields = fgetcsv($fh, null, ',', '"', '')) !== false) {
    $person = array_combine($header, $fields);
    echo "{$person['name']} lives in {$person['city']}: {$person['note']}\n";
}
fclose($fh);

Output:

name,city,note
Ada,London,"likes ""math"", a lot"
Linus,Helsinki,kernel

Ada lives in London: likes "math", a lot
Linus lives in Helsinki: kernel

Splitting lines with explode(',', $line) breaks as soon as a field contains a comma; fgetcsv() handles the quoting for you. For a semicolon-separated file (common in Excel exports in Europe), pass ';' as the separator.

Move around a file with fseek(), ftell() and rewind()

An open file has a position. Reads and writes start there and move it forward. ftell() tells you where it is, fseek() moves it to a byte offset, and rewind() goes back to the start. With w+ you can write a file and read it back through the same handle:

<?php
$fh = fopen('message.txt', 'w+');
fwrite($fh, 'hello world');
echo ftell($fh), "\n";             // after the last byte written

fseek($fh, 6);
echo fread($fh, 5), "\n";          // 5 bytes from offset 6

rewind($fh);
echo stream_get_contents($fh), "\n";  // everything from the position to the end
fclose($fh);

Output:

11
world
hello world

Lock a file with flock()

Two requests that read a counter, add one and write it back at the same time can both read 41 and both write 42. flock() with LOCK_EX makes the second one wait until the first releases the lock. Mode c+ is the right one here: it creates the file if needed and, unlike w+, does not empty it before you hold the lock.

<?php
function increment(string $path): int
{
    $fh = fopen($path, 'c+');
    flock($fh, LOCK_EX);               // wait for exclusive access

    $count = (int) stream_get_contents($fh);
    $count++;

    ftruncate($fh, 0);                 // empty the file
    rewind($fh);
    fwrite($fh, (string) $count);
    fflush($fh);

    flock($fh, LOCK_UN);
    fclose($fh);
    return $count;
}

for ($i = 0; $i < 3; $i++) {
    echo 'Visitor number ', increment('counter.txt'), "\n";
}

Output:

Visitor number 1
Visitor number 2
Visitor number 3

Locks are advisory: they only stop other code that also calls flock(). For appending one line, file_put_contents($path, $line, FILE_APPEND | LOCK_EX) does the same in one call.

Common mistake: while (!feof($fh))

Many old tutorials loop with feof(). It returns true only after a read has already hit the end, so the loop runs once more than there are lines and the last fgets() returns false:

<?php
file_put_contents('abc.txt', "a\nb\nc\n");

$fh = fopen('abc.txt', 'r');
$rounds = 0;
while (!feof($fh)) {
    $line = fgets($fh);
    $rounds++;
    var_dump($line);
}
fclose($fh);
echo "$rounds rounds for 3 lines\n";

Output:

string(2) "a
"
string(2) "b
"
string(2) "c
"
bool(false)
4 rounds for 3 lines

That extra false becomes an empty row in a report or an empty element in an array. Loop on the read itself, while (($line = fgets($fh)) !== false), as every other example on this page does.