add_action() function in wordpress not working [duplicate]

php css wordpress

PHP Snippet 1:

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

PHP Snippet 2:

/**
 * Proper way to enqueue scripts and styles
 */
function myFunction() {
    wp_enqueue_style( 'style-name', get_stylesheet_uri() );
    wp_enqueue_script( 'script-name', get_template_directory_uri() . '/js/example.js', array(), '1.0.0', true );
}
add_action( 'wp_enqueue_scripts', 'myFunction' );

PHP Snippet 3:

add_action( 'after_setup_theme', 'yourtheme_theme_setup' );

if ( ! function_exists( 'yourtheme_theme_setup' ) ) {
    function yourtheme_theme_setup() {

        add_action( 'wp_enqueue_scripts', 'yourtheme_scripts' );

    }
}

if ( ! function_exists( 'yourtheme_scripts' ) ) {
    function yourtheme_scripts() {

        wp_enqueue_style( 'main_style', get_stylesheet_uri(), array() );

    }
}

PHP Snippet 4:

<!DOCTYPE html>
<html>
  <head>
    <?php wp_head(); ?>
  </head>
  <body>
    ...
  </body>
</html>