A file to process 2 lists, removing the entries from the first list that occur in the second list, and creating a txt file with the resultant list

processCheckoutJs.php

<?php

$listOfFiles = 'assets_js.txt';
$listOfCheckoutFiles = 'assets_checkout_files.txt';
$outputOfNonCheckoutFiles = 'assets_non-checkout_files.txt';


$files = file($listOfFiles, FILE_IGNORE_NEW_LINES);
$checkoutFiles = file($listOfCheckoutFiles , FILE_IGNORE_NEW_LINES);
$nonCheckoutFiles = [];

// Loop all JS files that exist within Magento
foreach ($files as $file) {
    $inArray = false;

    // Check if the file being looped is a checkout file
    foreach ($checkoutFiles as $checkoutFile) {
        if (strstr($file, $checkoutFile)) {
            $inArray = true;
        }
    }

    // Only keep files that aren't used in checkout
    if (!$inArray) {
        // Remove the "{frontend|adminhtml}/{Vendor}/{ThemeName}/{locale}/" section from the names
        $pattern = "~([a-zA-Z]*/){3}([a-zA-Z_]*/)~";
        $nonCheckoutFiles[] = preg_replace($pattern, "", $file);;
    }
}


// Remove duplicate entries
$cleanedNonCheckoutFiles = array_unique($nonCheckoutFiles);

// Create file with appropriate XML elements
foreach ($cleanedNonCheckoutFiles as $file) {
    // Example of following replace: Magento_Theme/menu.min.js => Magento_Theme::menu.min.js
    $filename = preg_replace('~([A-Z][a-zA-Z]*_[A-Z][a-zA-Z]*)/~', '${1}::', $file);
    $string = '<item type="file">' . $filename . '</item>'.PHP_EOL;
    file_put_contents($outputOfNonCheckoutFiles, $string , FILE_APPEND | LOCK_EX);
}