AJAX Example

custom.js

(function ($) {
	$(document).ready(function () {
		$('#test').click(function () {
			$.ajaxSetup( { cache: false } );
			$.ajax( {
				type: 'POST',
				dataType: 'json',
				url: ajax.url,
				data: { 
					action: 'test_wp_action', 
					function: link.data( 'sample-data' ), 
					nextNonce: ajax.formNonce
				},
				success: function ( response ) {
					console.log(response);
					//load the fetched php file into the div
					$( '#div_id' ).html( response.content );
				}
			} );
			return false;
		});

	});
})(jQuery);

functions.php

add_action( 'wp_enqueue_scripts', 'custom_js_script' );
add_action( 'wp_ajax_test_wp_action', 'ajax_wp_action_func' );
add_action( 'wp_ajax_nopriv_test_wp_action', 'ajax_wp_action_func' );


function custom_js_script() {
	wp_enqueue_script( 'inputtitle_submit', get_template_directory_uri() . '/js/custom.js', array( 'jquery' ) );
	wp_localize_script( 'inputtitle_submit', 'ajax', array(
			'url'   => admin_url( 'admin-ajax.php' ),
			'nextNonce' => wp_create_nonce( 'sample-ajax-next-nonce' )
		)
	);
}

function ajax_wp_action_func() {

	// check nonce
	$nonce = $_POST['formNonce'];
	if ( ! wp_verify_nonce( $nonce, 'sample-ajax-next-nonce' ) ) {
		return;
	}
	
	$response = wp_send_json( $_POST );
	die();
}