PMPro Approvals, add an approve/deny link to one click action the pending member from email.

pmpro-approvals-email-approve-deny.php

<?php
/**
 * Creates {{approve_action_link}} and {{deny_action_link}} for pending emails.
 * Only add it to the pending approval (admin) email template.
 * Add this code to your site by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

/**
 * Build the frontend URL for an email-based approval or denial action.
 *
 * @param int    $user_id  The member's user ID.
 * @param int    $level_id The membership level ID.
 * @param string $action   'approve' or 'deny'.
 * @return string The full URL.
 */
function my_pmpro_get_approval_action_url( $user_id, $level_id, $action ) {
	return add_query_arg( array(
		'pmpro_email_approval' => $action,
		'pmpro_member'         => $user_id,
		'pmpro_level'          => $level_id,
	), home_url( '/' ) );
}

/**
 * Inject !!approve_action_link!! and !!deny_action_link!! variables into the
 * admin pending notification email. This filter runs for both the legacy email
 * class and the newer PMPro_Email_Template system.
 */
function my_pmpro_approvals_add_action_links( $data, $member, $admin ) {
	if ( empty( $member ) || ! isset( $data['membership_id'] ) ) {
		return $data;
	}
	$level_id = intval( $data['membership_id'] );
	if ( $level_id < 1 ) {
		return $data;
	}

	if ( ! class_exists( 'PMPro_Approvals' ) || ! PMPro_Approvals::requiresApproval( $level_id ) ) {
		$data['approve_action_link'] = '';
		$data['deny_action_link']    = '';
		return $data;
	}
	$data['approve_action_link'] = my_pmpro_get_approval_action_url( $member->ID, $level_id, 'approve' );
	$data['deny_action_link']    = my_pmpro_get_approval_action_url( $member->ID, $level_id, 'deny' );
	return $data;
}
add_filter( 'pmpro_approvals_admin_pending_email_data', 'my_pmpro_approvals_add_action_links', 10, 3 );


/**
 * Process an email-based approval/denial on page load. Requires the user to
 * be logged in with the pmpro_approvals capability; redirects to login otherwise.
 */
function my_pmpro_process_email_approval_action() {
	if ( empty( $_GET['pmpro_email_approval'] ) ) {
		return;
	}

	$action   = sanitize_key( $_GET['pmpro_email_approval'] );
	$user_id  = isset( $_GET['pmpro_member'] ) ? intval( $_GET['pmpro_member'] ) : 0;
	$level_id = isset( $_GET['pmpro_level'] ) ? intval( $_GET['pmpro_level'] ) : 0;

	if ( ! in_array( $action, array( 'approve', 'deny' ), true ) || ! $user_id || ! $level_id ) {
		wp_die( 'Invalid approval request.', 'Error', array( 'response' => 400 ) );
	}

	if ( ! is_user_logged_in() ) {
		wp_safe_redirect( wp_login_url( add_query_arg( $_GET, home_url( '/' ) ) ) );
		exit;
	}

	$capability = current_user_can( 'pmpro_approvals' ) ? 'pmpro_approvals' : 'manage_options';
	if ( ! current_user_can( $capability ) ) {
		wp_die( 'You do not have permission to perform this action.', 'Error', array( 'response' => 403 ) );
	}

	if ( ! class_exists( 'PMPro_Approvals' ) ) {
		wp_die( 'PMPro Approvals plugin is not active.', 'Error', array( 'response' => 500 ) );
	}

	$member    = get_user_by( 'ID', $user_id );
	$name      = $member ? $member->display_name : "User #{$user_id}";

	if ( 'approve' === $action ) {
		PMPro_Approvals::approveMember( $user_id, $level_id );
		$notice = 'approved';
	} else {
		PMPro_Approvals::denyMember( $user_id, $level_id );
		$notice = 'denied';
	}

	wp_safe_redirect( add_query_arg( array(
		'page'                  => 'pmpro-approvals',
		'pmpro_approval_notice' => $notice,
		'pmpro_approval_name'   => rawurlencode( $name ),
	), admin_url( 'admin.php' ) ) );
	exit;
}
add_action( 'init', 'my_pmpro_process_email_approval_action' );

/**
 * Display an admin notice on the approvals page after an email-based action.
 * Function name must start with "pmpro" to survive PMPro's notice filter.
 */
function pmpro_approval_email_action_notice() {
	if ( empty( $_GET['page'] ) || $_GET['page'] !== 'pmpro-approvals' ) {
		return;
	}
	if ( empty( $_GET['pmpro_approval_notice'] ) ) {
		return;
	}

	$notice = sanitize_key( $_GET['pmpro_approval_notice'] );
	$name   = isset( $_GET['pmpro_approval_name'] ) ? esc_html( rawurldecode( $_GET['pmpro_approval_name'] ) ) : 'Member';

	if ( 'approved' === $notice ) {
		$type = 'success';
		$text = "<strong>{$name}</strong> has been approved.";
	} elseif ( 'denied' === $notice ) {
		$type = 'warning';
		$text = "<strong>{$name}</strong> has been denied.";
	} else {
		return;
	}

	echo "<div class='notice notice-{$type} is-dismissible'><p>{$text}</p></div>";
}
add_action( 'admin_notices', 'pmpro_approval_email_action_notice' );