To implement the drop-down menu multiple selection function in HTML, 1. Add the multiple attribute to the
In web development, if you want users to select multiple options from the drop-down menu, the HTML select
element can easily achieve this function with multiple
attributes. Just add this attribute to let the user hold down Ctrl (or Command on Mac) to perform multiple selections.

How to use multiple
attributes
To enable the multi-select function, just add multiple
attribute to the <select></select>
tag:
<select multiple> <option value="option1">Option 1</option> <option value="option2">Option 2</option> <option value="option3">Option 3</option> </select>
In this way, the browser will render a drop-down box that can be selected multiple times. Users can select multiple options by clicking and cooperating with the Ctrl key. Note that the drop-down box will become a list box style at this time, rather than the traditional drop-down menu.

How to submit data when multiple selections
When a form is submitted, multiple selected values are sent to the server as an array. For example, if you use PHP to receive data, you can obtain multiple values by:
$selected = $_POST['selectName']; foreach ($selected as $value) { echo $value . '<br>'; }
When processing backend, make sure the field name has []
, for example:

<select name="colors[]" multiple> <option value="red">Red</option> <option value="blue">blue</option> <option value="green">Green</option> </select>
This way the server side can correctly receive multiple values.
How to get selected values through JavaScript
If you want to use JavaScript to get multiple currently selected values, you can use the following methods:
- Use
querySelectorAll
to get all selected options:
const selectedOptions = document.querySelectorAll('select[multiple] option:checked'); const values = Array.from(selectedOptions).map(option => option.value); console.log(values);
- Or through
HTMLSelectElement.selectedOptions
property:
const selectElement = document.querySelector('select[multiple]'); const selected = Array.from(selectElement.selectedOptions).map(opt => opt.value); console.log(selected);
These methods can help you dynamically obtain user selection results on the front-end.
Common precautions
- Display style differences : The appearance of the multi-select drop-down box may be slightly different under different browsers. It is recommended to customize the styles through CSS or JavaScript plug-ins if necessary.
- Mobile compatibility : On mobile devices, the native multi-select drop-down box experience may not be good, and some devices do not even support click multi-select. If mobile support is required, it is best to use third-party components (such as Select2 or Bootstrap Multiselect).
- Not expanded by default : If you want all options to be expanded by default when the page is loaded, additional JavaScript or CSS control is required.
Basically that's it. This function is not complicated, but it is easy to ignore details in actual development, such as how the backend receives data, mobile compatibility issues, etc., which need to be paid attention to.
The above is the detailed content of HTML `select` `multiple` Attribute for Multi-Selection. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

The rational use of semantic tags in HTML can improve page structure clarity, accessibility and SEO effects. 1. Used for independent content blocks, such as blog posts or comments, it must be self-contained; 2. Used for classification related content, usually including titles, and is suitable for different modules of the page; 3. Used for auxiliary information related to the main content but not core, such as sidebar recommendations or author profiles. In actual development, labels should be combined and other, avoid excessive nesting, keep the structure simple, and verify the rationality of the structure through developer tools.

To use HTML button elements to achieve clickable buttons, you must first master its basic usage and common precautions. 1. Create buttons with tags and define behaviors through type attributes (such as button, submit, reset), which is submitted by default; 2. Add interactive functions through JavaScript, which can be written inline or bind event listeners through ID to improve maintenance; 3. Use CSS to customize styles, including background color, border, rounded corners and hover/active status effects to enhance user experience; 4. Pay attention to common problems: make sure that the disabled attribute is not enabled, JS events are correctly bound, layout occlusion, and use the help of developer tools to troubleshoot exceptions. Master this

Metadata in HTMLhead is crucial for SEO, social sharing, and browser behavior. 1. Set the page title and description, use and keep it concise and unique; 2. Add OpenGraph and Twitter card information to optimize social sharing effects, pay attention to the image size and use debugging tools to test; 3. Define the character set and viewport settings to ensure multi-language support is adapted to the mobile terminal; 4. Optional tags such as author copyright, robots control and canonical prevent duplicate content should also be configured reasonably.

TolearnHTMLin2025,chooseatutorialthatbalanceshands-onpracticewithmodernstandardsandintegratesCSSandJavaScriptbasics.1.Prioritizehands-onlearningwithstep-by-stepprojectslikebuildingapersonalprofileorbloglayout.2.EnsureitcoversmodernHTMLelementssuchas,

Using HTML sums allows for intuitive and semantic clarity to add caption text to images or media. 1. Used to wrap independent media content, such as pictures, videos or code blocks; 2. It is placed as its explanatory text, and can be located above or below the media; 3. They not only improve the clarity of the page structure, but also enhance accessibility and SEO effect; 4. When using it, you should pay attention to avoid abuse, and apply to content that needs to be emphasized and accompanied by description, rather than ordinary decorative pictures; 5. The alt attribute that cannot be ignored, which is different from figcaption; 6. The figcaption is flexible and can be placed at the top or bottom of the figure as needed. Using these two tags correctly helps to build semantic and easy to understand web content.

How to make HTML mail templates with good compatibility? First, you need to build a structure with tables to avoid using div flex or grid layout; secondly, all styles must be inlined and cannot rely on external CSS; then the picture should be added with alt description and use a public URL, and the buttons should be simulated with a table or td with background color; finally, you must test and adjust the details on multiple clients.

class, id, style, data-, and title are the most commonly used global attributes in HTML. class is used to specify one or more class names to facilitate style setting and JavaScript operations; id provides unique identifiers for elements, suitable for anchor jumps and JavaScript control; style allows for inline styles to be added, suitable for temporary debugging but not recommended for large-scale use; data-properties are used to store custom data, which is convenient for front-end and back-end interaction; title is used to add mouseover prompts, but its style and behavior are limited by the browser. Reasonable selection of these attributes can improve development efficiency and user experience.

When there is no backend server, HTML form submission can still be processed through front-end technology or third-party services. Specific methods include: 1. Use JavaScript to intercept form submissions to achieve input verification and user feedback, but the data will not be persisted; 2. Use third-party serverless form services such as Formspree to collect data and provide email notification and redirection functions; 3. Use localStorage to store temporary client data, which is suitable for saving user preferences or managing single-page application status, but is not suitable for long-term storage of sensitive information.
