Writing Files

To write to a file, open it with a write mode and use fwrite().

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<?php
$handle = fopen("greeting.txt", "w");

fwrite($handle, "Hello, file!\n");
fwrite($handle, "This is the second line.\n");

fclose($handle);

echo file_get_contents("greeting.txt");

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Hello, file!
This is the second line.

fwrite() writes exactly the text you give it. It does not add a new line, so include \n yourself.

The w mode empties the file

When you open a file in w mode, PHP deletes the old content immediately, before you write anything.

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<?php
file_put_contents("data.txt", "old content that matters");

$handle = fopen("data.txt", "w");   // the old content is already gone
fclose($handle);

var_dump(filesize("data.txt"));

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int(0)

If you want to keep what is there and add to it, use append mode, covered in the next lesson.

fwrite() returns the number of bytes

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<?php
$handle = fopen("count.txt", "w");

$bytes = fwrite($handle, "abc");

fclose($handle);

var_dump($bytes);

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int(3)

fwrite() returns false if writing failed (disk full, no permission). Check it when the data matters.

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<?php
if (fwrite($handle, $text) === false) {
    // log the problem and tell the user
}

Write several lines

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<?php
$lines = ["name,age", "Ana,30", "Ben,25"];

$handle = fopen("people.csv", "w");

foreach ($lines as $line) {
    fwrite($handle, $line . PHP_EOL);
}

fclose($handle);

echo file_get_contents("people.csv");

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name,age
Ana,30
Ben,25

PHP_EOL is the correct line ending for the current system.

fputs()

fputs() is an alias for fwrite(). Use fwrite(), which is the common name.

Never overwrite by accident: mode x

Mode x creates a file and fails if it already exists. It protects existing files.

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<?php
file_put_contents("report.txt", "existing");

$handle = @fopen("report.txt", "x");

var_dump($handle);

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bool(false)

Permissions

The user that runs PHP (for example www-data) needs permission to write to the folder. If you see “failed to open stream: Permission denied”, fix the folder permissions. Do not make folders world-writable (777) on a real server.