Image Resizing in PHP (Create Thumbnails Safely)

Uploading a 6MB image and showing it directly is a performance killer. Professional apps generate thumbnails. ## Common tools - GD library (built-in in many PHP installs) - Imagick (powerful if available) ## Example (GD, JPEG to thumbnail) ```php <?php $srcPath = __DIR__ . "/uploads/source.jpg"; $dstPath = __DIR__ . "/uploads/thumb.jpg"; $src = imagecreatefromjpeg($srcPath); $srcW = imagesx($src); $srcH = imagesy($src); $thumbW = 300; $thumbH = (int)($srcH * ($thumbW / $srcW)); $thumb = imagecreatetruecolor($thumbW, $thumbH); imagecopyresampled($thumb, $src, 0, 0, 0, 0, $thumbW, $thumbH, $srcW, $srcH); imagejpeg($thumb, $dstPath, 85); imagedestroy($src); imagedestroy($thumb); ?> ``` ## Why quality 85 Good balance between size and clarity. > Next: CSRF protection for APIs and cookies-based auth (advanced detail).