What are the potential pitfalls of generating images at runtime in PHP, as seen in the provided script for a photo gallery?

One potential pitfall of generating images at runtime in PHP is the performance impact it can have on the server, especially if a large number of images need to be generated. To solve this issue, one approach is to generate and cache the images on the server side, so they can be served quickly without the need for repeated generation.

// Check if the image exists in the cache directory
$cacheFile = 'cache/' . md5($imagePath) . '.jpg';

if (!file_exists($cacheFile)) {
    // Generate the image if it doesn't exist in the cache
    // Your image generation code here
    
    // Save the generated image to the cache directory
    imagejpeg($imageResource, $cacheFile);
}

// Serve the cached image
header('Content-Type: image/jpeg');
readfile($cacheFile);