#utility for finding callback functions hooked to a specific hook

find_callback.php

<?php // do not use this line. Add below to functions.php


add_action( 'wp_footer', 'list_hooked_filters_and_actions' );
add_action( 'login_footer', 'list_hooked_filters_and_actions' );
add_action( 'admin_footer', 'list_hooked_filters_and_actions' );

function list_hooked_filters_and_actions() {
    global $wp_filter;

	$hook = 'login_form';
	
    if( empty( $hook ) || !isset( $wp_filter[$hook] ) )
        return;

	echo '<div style="background-color:#D3D3D3;min-height:200px;">';
	echo '<h2>Callbacks hooked to "' . $hook . '"</h2><ul>';
	foreach( $wp_filter[ $hook ]->callbacks as $key => $priority ) {
		
		foreach ( $priority as $callback => $details ) {
			echo '<li>' . $details['function'] . ' priority: ' . $key . '</li>';
		}

	}
	echo '</ul></div>';
}