How to create a file if it does not exist in PHP?

To create a file in PHP if it does not exist, you can use the fopen function with the x mode. This function tries to create the file and open it for writing, and returns a file handle if it was successful.

Here’s an example:

$filename = 'file.txt';
$handle = fopen($filename, 'x');

if ($handle !== false) {
    // The file was created and is now open for writing
    fwrite($handle, 'Hello, world!');
    fclose($handle);
} else {
    // The file already exists or could not be created
}

Note that the x mode is only available in PHP 5.4 and later. In older versions, you can use the fopen function with the w mode to open the file for writing, and then use the file_exists function to check if the file already exists. If it does, you can use the fopen function with the a mode to open the file for appending instead:

$filename = 'file.txt';
if (!file_exists($filename)) {
    $handle = fopen($filename, 'w');
} else {
    $handle = fopen($filename, 'a');
}

if ($handle !== false) {
    fwrite($handle, 'Hello, world!');
    fclose($handle);
} else {
    // There was an error opening the file
}