how to add version of style.css in wordpress

You don't need in fact to un cache the style.css file.

You can write your own css file then queue like the way @vinod dalvi has written.

function theme_styles()  
{ 
  wp_enqueue_style('stylecss',get_template_directory_uri().'/yourname.css', array(), '1.2', 'all' );
}
add_action('wp_enqueue_scripts', 'theme_styles');

Based on browser rules the latest css file has higher priority , so make sure to use !important in your css code if necessary .

Good luck.

Here we use WordPress’ wp_get_theme() to get the theme version (as specified in the theme’s stylesheet, style.css):

// get theme version
function rave_get_version() {
    $theme_data = wp_get_theme();
    return $theme_data->Version;
}
$theme_version = rave_get_version();
global $theme_version;

wp_enqueue_style( 'main-style', get_template_directory_uri() .'/assets/css/style.css', [], THEME_VERSION, 'all' );

Another solution if you can't figure it out yet, it's to change the filename of your child theme's style.css to, for example, style2.css and then change it on your child theme's functions.php file, as shown below:

wp_enqueue_style( 'style', get_stylesheet_directory_uri() .'/style2.css' );

This will cause Wordpress to request and serve a new CSS file for your website.

Contrary to the methods presented so far, I believe it is better to use the version number which appears at the top of your style.css file:

// style.css
/**
Theme Name: My theme
...
Version: 1.2.3
...
**/

To use the theme's version in your css, add the following to your functions.php (or equivalent) script:

<?php

wp_enqueue_style(
    'my-theme',
    get_stylesheet_directory_uri() . '/style.css',
    [],
    wp_get_theme()->get('Version')
);

This means that, after you edit your style.css file, all you need to do is to change the version number at the top of the same file to see the changes in the frontend.

If you examine the head section of the theme's HTML you will see the following:

<link rel='stylesheet'
    id='my-theme-css'
    href='... style.css?ver=1.2.3'
    type='text/css'
    media='all'
/>

If you are a theme developer, you might want to force reload of your assets when you push new version.

So versioning of a theme is done in style.css

/*
    Theme Name: Your Theme Name
    Version: 1.0.2
*/

At the top of your functions.php:

$theme = wp_get_theme();
define('THEME_VERSION', $theme->Version); //gets version written in your style.css

Later when you enqueue CSS or JS, use THEME_VERSION as fourth argument:

function theme_styles()
{
    wp_enqueue_style('main', get_template_directory_uri().'/css/main.css', [], THEME_VERSION, 'all');
}
add_action('wp_enqueue_scripts', 'theme_styles'); 

Will output to the page:

.../your-theme-name/css/main.css?ver=1.0.2 

Gets handy when you have more assets to care about and don't want to change them manually.

Instead of hardwiring the version, you might find it better in some instances to dynamically version your stylesheet so whenever you change it, it automatically changes and refreshes the browser cache immediately without having to edit your functions.php over and over again.

You can use filemtime() to do that. Here is how to do that in a child-style that references the parent_style

    wp_enqueue_style( 'child-style', get_stylesheet_directory_uri() . '/style.css', array( $parent_style ), filemtime( get_stylesheet_directory() . '/style.css' )  );

Try this:

Add this to functions.php

function autoVer($filename){
    $url = get_template_directory_uri() . $filename;
    $file = get_template_directory() . $filename;
    if ( file_exists($file)) {
        return $url . '?v=' .md5(date("FLdHis", filectime($file)) . filesize($file));
    }
    clearstatcache();
}

Add this to the header or footer -> autoVer('/js/main.js');

the best way to load css into your wordpress theme is the following code in your functions.php file:

function theme_styles()  
{ 
  global $ver_num; // define global variable for the version number
  $ver_num = mt_rand() // on each call/load of the style the $ver_num will get different value
  wp_enqueue_style( 'style-css', get_template_directory_uri() . '/style.css', array(), $ver_num, 'all' );
}
add_action('wp_enqueue_scripts', 'theme_styles');

This is the right way to load the styles in your theme and also it's the best for staging/testing purposes because each refresh will deliver the updated version of the style.

If you want to avoid the loading 1st way, you can use this shorted version and place the following line into your header.php file and will get the same result:

<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); echo '?ver=' . filemtime( get_stylesheet_directory() . '/style.css'); ?>" type="text/css" media="screen, projection" />

Cheers

This is pretty straight up way of getting the version number by calling the function bloginfo($show) twice. First for the stylesheet and secondly for the version number.

<link rel="stylesheet" id="style-css" href="<?php bloginfo('stylesheet_url'); ?>?ver=<?php bloginfo('version'); ?>" type="text/css" media="all" />

Thats all there is to it. Hope that helps or is useful. You can go through all the parameters available and see what you can output with the bloginfo() function.

Ignore my comment since @Ravs has pointed out my error regarding the 'versions' parameter for the bloginfo() function. It does indeed print the Wordpress version number.

You can achieve this using one of the following ways :

1) Add following tag in header.php file of the theme.

<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>'?v=1.2" type="text/css" media="all" />

2) Add following code in functions.php file of the theme.

function theme_styles()  
{ 
  // Register the style like this for a theme:  
  // (First the unique name for the style (custom-style) then the src, 
  // then dependencies and ver no. and media type)
  wp_enqueue_style( 'style-css', get_template_directory_uri() . '/style.css', array(), '1.2', 'all' );
}
add_action('wp_enqueue_scripts', 'theme_styles');

For more information see this page.

Version number is a parameter of wp_enqueue_style().

As per the Codex, here are all the parameters that wp_enqueue_style accepts.

wp_enqueue_style( $handle, $src, $deps, $ver, $media );

So for example to load a stylesheet with a version number you'd do the following:

function wpa_90820() {
    wp_enqueue_style('my-styles', get_stylesheet_directory_uri() .'/my-styles.css', array(), '1.0' );       
}

add_action('wp_enqueue_scripts', 'wpa_90820');