PHP SplFileObject fflush() Function

The SplFileObject::fflush() function is an inbuilt function in the Standard PHP Library (SPL) in PHP that is used to flush the output buffer of the file.

Syntax:

public SplFileObject::fflush():bool

Parameter: This function does not accept any parameters.

Return Value: The SplFileObject::fflush() function returns "true" if the function successfully flushes the output buffer of the file otherwise, this function will return "false".

Program 1: The following program demonstrates the SplFileObject::flush() function. The "output.txt" should be available in the same folder.

<?php

$file = new SplFileObject("output.txt", "w");

$data = "This is some data that will be written to the file.\n";

$file->fwrite($data);

// Flush the data to the file immediately
if ($file->fflush()) {
    echo "Data flushed successfully to the file.";
} else {
    echo "Failed to flush data to the file.";
}

?>

Output:

Data flushed successfully to the file.

Program 2: The following program demonstrates SplFileObject::flush() function. The "output.txt" should be available in the same folder.

<?php

$file = new SplFileObject("output.txt", "w");

$dataLines = [
    "Line 1: This is the first line of data.\n",
    "Line 2: This is the second line of data.\n",
    "Line 3: This is the third line of data.\n",
];

foreach ($dataLines as $line) {
    
    // Write the line to the file
    $file->fwrite($line);

    // Flush the data to the file
    // immediately after writing each line
    if ($file->fflush()) {
        echo "Data flushed successfully for line: " . $line;
    } else {
        echo "Failed to flush data for line: " . $line;
    }
}

?>

Output:

Data flushed successfully for line: Line 1: This is the first line of data.
Data flushed successfully for line: Line 2: This is the second line of data.
Data flushed successfully for line: Line 3: This is the third line of data.

Reference: https://www.php.net/manual/en/splfileobject.fflush.php