Scan images in bacth and store to json file.

fp-scan-images-batch-v3.php

<?php

// Scan images in batch
function fp_image_scan_batch($batch_size = 500, $reset = false)
{
    $upload_dir = wp_get_upload_dir();
    $batch      = [];
    $log_file   = trailingslashit(WP_CONTENT_DIR) . 'fp-image-scan.log';

    // Reset log file on first batch
    if($reset || !file_exists($log_file)) {
        file_put_contents($log_file, "");
    }

    // Get already logged images
    $logged = file($log_file, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    if(!is_array($logged)) {
        $logged = [];
    }

    $lookup = array_flip($logged); // Make a lookup for O(1) checks

    $iterator = new RecursiveIteratorIterator(
        new RecursiveDirectoryIterator($upload_dir['basedir'], FilesystemIterator::SKIP_DOTS)
    );

    foreach($iterator as $file){
        if($file->isFile() && in_array(strtolower($file->getExtension()), ['jpg', 'jpeg', 'png'], true)){
            $link = str_replace($upload_dir['basedir'], $upload_dir['baseurl'], $file->getPathname());

            // Skip already logged images
            if (isset($lookup[$link])) {
                continue;
            }

            $batch[] = $link;

            if (count($batch) >= $batch_size) {
                break;
            }
        }
    }

    if(!empty($batch)){
        $log_content = implode(PHP_EOL, $batch) . PHP_EOL;
        error_log($log_content, 3, $log_file);
    }
}