Ajax in WordPress

ajax-action.php

add_action( 'wp_ajax_button_click', 'user_clicked' );
function user_clicked() {
    update_user_meta( get_current_user_id(), 'clicked_link', 'yes' );
    wp_redirect( $_SERVER['HTTP_REFERER'] );
    exit();
}

ajax-function.php

add_action( 'wp_ajax_button_click', 'user_clicked' );
function user_clicked() {
    update_user_meta( get_current_user_id(), 'clicked_link', 'yes' );
    echo 'ok';
    die();
}

ajax-js.js

jQuery(document).on( 'click', '#button', function() {
    var button = jQuery(this);
    var url = button.attr('href');
    
    jQuery.ajax({
        type : 'post',
        url : url,
        data : {
            action : 'user_clicked'
        },
        success : function( response ) {
            if( response === 'ok' ) {
                button.fadeOut( function() {
                    button.replaceWith( 'already clicked' );
                })
            }
        }
    });
    
    return false;
})

button-ajax.php

if ( is_user_logged_in() ) {
    if ( has_user_clicked_link() ) {
        echo "already clicked";
    }
    else {
        echo "<a id='button' href='" . admin_url('admin-ajax.php?action=button_click') . "'>Click here now</a>";
    }
}

button.php

if ( is_user_logged_in() ) {
    if ( has_user_clicked_link() ) {
        echo "already clicked";
    }
    else {
        echo "<a id='button' href='?button_click=true'>Click here now</a>";
    }
}

enqueue.php

function ajax_search_enqueues() {
    if ( is_search() ) {
    	wp_enqueue_script( 'ajax-search', get_stylesheet_directory_uri() . '/js/ajax-search.js', array( 'jquery' ), '1.0.0', true );
        wp_localize_script( 'ajax-search', 'myAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );

    	wp_enqueue_style( 'ajax-search', get_stylesheet_directory_uri() . '/css/ajax-search.css' );
    }
}

add_action( 'wp_enqueue_scripts', 'ajax_search_enqueues' );

fallback.php

add_action( 'wp_ajax_button_click', 'user_clicked' );
function user_clicked() {
    update_user_meta( get_current_user_id(), 'clicked_link', 'yes' );
    if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
        echo 'ok';
        die();
    }
    else {
        wp_redirect( $_SERVER['HTTP_REFERER'] );
        exit();
    }
}

has_clicked.php

function has_user_clicked_link() {
    if( 'yes' == get_user_meta( get_current_user_id(), 'clicked_link', true ) ) {
        return true;
    }
    
    return false;
}

search-action.php

add_action( 'wp_ajax_load_search_results', 'load_search_results' );
add_action( 'wp_ajax_nopriv_load_search_results', 'load_search_results' );

function load_search_results() {
    $query = $_POST['query'];
    
    $args = array(
        'post_type' => 'post',
        'post_status' => 'publish',
        's' => $query
    );
    $search = new WP_Query( $args );
    
    ob_start();
    
    if ( $search->have_posts() ) : 
    
    ?>

		<header class="page-header">
			<h1 class="page-title"><?php printf( __( 'Search Results for: %s', 'twentyfourteen' ), get_search_query() ); ?></h1>
		</header>

		<?php
			while ( $search->have_posts() ) : $search->the_post();

				get_template_part( 'content', get_post_format() );

			endwhile;
			twentyfourteen_paging_nav();

	else :
		get_template_part( 'content', 'none' );
	endif;
	
	$content = ob_get_clean();
	
	echo $content;
	die();
			
}

search.js

jQuery(document).on( 'submit', '#search-container form', function() {
    var $form = jQuery(this);
    var $input = $form.find('input[name="s"]');
    var query = $input.val();
    var $content = jQuery('#content')
    
    jQuery.ajax({
        type : 'post',
        url : myAjax.ajaxurl,
        data : {
            action : 'load_search_results',
            query : query
        },
        beforeSend: function() {
            $input.prop('disabled', true);
            $content.addClass('loading');
        },
        success : function( response ) {
            $input.prop('disabled', false);
            $content.removeClass('loading');
            $content.html( response );
        }
    });
    
    return false;
})

set-meta.php

add_action( 'init', 'user_clicked' );
function user_clicked() {
    if( is_user_logged_in() && !empty( $_GET['button_click'] ) && $_GET['button_click'] == 'true' ) {
        update_user_meta( get_current_user_id(), 'clicked_link', 'yes' );
    }
}

style.css

#content.loading > * {
    opacity:0.2;
}

#content.loading:before {
    content: "Loading New Posts";
    padding: 22px;
    background: #000;
    color: #fff;
    width: 100%;
    box-sizing: border-box;
}