This article demonstrates how to upload images using Ajax and display a thumbnail preview without page reloads. The process involves client-side JavaScript for handling the upload and a PHP backend for thumbnail generation and image storage.

Client-Side (JavaScript):

The core functionality resides in the uploadImage function, which uses $.ajaxFileUpload to send the image to the server. Upon successful upload, the server returns JSON data containing the URLs for both the original and thumbnail images. The JavaScript then updates the src attribute of the image elements (#image-thumb, representing the preview) to display the thumbnail. Error handling and loading indicators are also included.

uploadImage: function() {
    // ... (Existing code) ...
    $.ajaxFileUpload({
        // ... (Existing code) ...
        success: function(data) {
            // Update image preview
            _this.cache.$imgPreview.attr('src', data.thumb.img_src);
            _this.cache.$imgOriginal.attr('src', data.master.img_src);
            // ... (Existing code) ...
        },
        error: function(xhr, textStatus, errorThrown) {
            // ... (Existing code) ...
        },
        complete: function() {
            // ... (Existing code) ...
        }
    });
}

The image preview element is initially set with a placeholder image:

<img src="/static/imghw/default1.png"  data-src="https://img.php.cn/upload/article/000/000/000/174036625652715.jpg"  class="lazy" alt="jQuery AJAX Image Upload Thumbnail Example " />

Form submission includes the thumbnail's src attribute:

submitForm: function() {
    // ... (Existing code) ...
    formData += '&image-thumb=' + $('#image-thumb').attr('src');
    // ... (Existing code) ...
}

Server-Side (PHP):

The PHP script receives the uploaded image, generates a thumbnail using a suitable image manipulation library (e.g., GD or ImageMagick), and returns the URLs of both the original and thumbnail images as JSON. The images are initially saved to a temporary directory and moved to the final location upon form submission.

Security Considerations:

The script emphasizes the importance of setting appropriate file permissions (e.g., 774) on the image directory to prevent unauthorized access. Further security measures, such as file type validation and size limits, are recommended.

Frequently Asked Questions (FAQs):

The article concludes with a FAQ section addressing common concerns regarding multiple image uploads, progress bars, file validation, error handling, image resizing, form-less uploads, security, database storage, image display, and image deletion. These FAQs provide valuable insights into best practices for robust image upload functionality. The solutions proposed leverage various techniques like the HTML5 File API, Canvas API, and server-side validation.

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