Log $_GET or $_POST data to a CSV file. Example: index.php?bar=bar&foo=foo&baz=baz&bad-data=dont-save would append the following to the data.csv file: 1698022463,foo,bar,baz

index.php

<?php
// Merge the expected data with the data recieved
$expected_data = array(
    'timestamp' => '',
    'foo' => '',
    'bar' => '',
    'baz' => '',
);
$data = array_merge( $expected_data, $_REQUEST );

// Filter out any extra keys that might be passed in
$data = array_intersect_key( $data, $expected_data );

// If the data is empty then bail
if ( empty( $data ) ) {
    return;
}
// Set the timestamp value to the current time
$data['timestamp'] = time();

// Append the data to a CSV file
$handle = fopen( 'data.csv', 'a' );
fputcsv( $handle, $data );
fclose( $handle );