通过按钮单击调用时功能无法正常执行

I have an ajax request that looks like this:

  $('#clear_cache').click(function (event) {
      event.preventDefault();
      var ajaxurl = "clearcache.php";
      $.post(ajaxurl, function () {
          $('<p>The cache was cleared successfully.</p>').insertAfter('#clear_cache');
      });
  });

The clearcache.php file looks like this:

do_action( 'clear_terms', 'clear_transients' );

function clear_transients() {
global $wpdb;
$sql = "delete from {$wpdb->options}
where option_name like '_transient_cc%'";
return $wpdb->query($sql);
}

I know the ajax request is linking ok to the php file because when I clear out the php file and click on my button the request is made. I feel like there's something wrong with my PHP file, like the function hasn't been setup correctly or I am making the wrong request type. However when I tested out this php code out in the same file as where my button is located it works ok (but this was using a query string method). Your help is much appreciated.

I see a couple things wrong here. If you are using ajax with WordPress you should be running it through the admin ajax url.

You aren't using do_action properly. The first parameter is the name of the action and the second should be the arguments for the action. I think you are confusing do_action with add_action.

It's best practice to use die() or better yet wp_die() when you finish your ajax handler. Alternatively if you are returning some output you can use wp_send_json()

Your ajaxurl should always point to the admin-ajax.php. If you are doing this on the admin side ajaxurl is already setup for you. If you are doing this on the frontend you should have a snippet like the following in your functions.php

add_action( 'wp_enqueue_scripts', 'my_scripts' );

function my_scripts() {
    // the file where your javascript is located    
    wp_enqueue_script( 'ajax-script', get_template_directory_uri() . '/js/script.js', array('jquery') );

    // this makes the admin url available to your javascript
    wp_localize_script( 'ajax-script', 'ajax_object',
            array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );
}

You can then use ajax_object.ajaxurl in your javascript to get the right URL.

Your javascript may now look something like this:

$('#clear_cache').click(function (event) {
      event.preventDefault();
      var data = { action: 'clear_transients' }
      $.post( ajax_object.ajaxurl, data, function () {
          $('<p>The cache was cleared successfully.</p>').insertAfter('#clear_cache');
      });
  });

If you are running this in the admin just replace ajax_object.ajaxurl with ajaxurl. Notice the addition of the data variable. This will tell WordPress which action it should be running.

For your actions you should be using the wp_ajax_(action) for admin side or the wp_ajax_nopriv_(action) for the frontend.

This would change your ajax handler function to something like this:

// run on the admin side
add_action( 'wp_ajax_clear_transients', 'clear_transients' );

// or run on the frontend
add_action( 'wp_ajax_nopriv_clear_transients', 'clear_transients' );

function clear_transients() {
    global $wpdb;
    $sql = "DELETE FROM {$wpdb->options} WHERE option_name LIKE '_transient_cc%'";
    $wpdb->query($sql);
    wp_die();
}

Your ajax handler can also be placed in the functions.php.

One thing I did not mention is nonces. You should be using nonces for security. Nonces are used with check_ajax_referer to make sure ajax requests are originating from the correct source.

Looks like you are using Wordpress but the Ajax call goes to the php file directly without bootstrapping the required Wordpress files before.

Have a look here for instructions on using Ajax with Wordpress: https://codex.wordpress.org/AJAX_in_Plugins