如何使用 WP_Error 类进行 WordPress 错误处理（二）

<?php
/*
 Plugin Name: Contact Form Lite
 Plugin URI: http://code.tutsplus.com
 Description: Easy contact form plugin
 Author: Agbonghama Collins
 Author URI: http://tech4sky.com
 */

function contact_html_form() {
    global $name, $email, $phone_number, $subject, $message;

    echo '<form action="' . get_permalink() . '" method="post">

    <label for="name">Name <strong>*</strong></label>
    <input type="text" name="sender_name" value="' . ( isset( $_POST['sender_name'] ) ? $name : null ) . '" />

    <div>
    <label for="email">Email <strong>*</strong></label>
    <input type="text" name="sender_email" value="' . ( isset( $_POST['sender_email'] ) ? $email : null ) . '" />
    </div>

    <div>
    <label for="phonenumber">Phone Number <strong>*</strong></label>
    <input type="text" name="sender_phonenumber" value="' . ( isset( $_POST['sender_phonenumber'] ) ? $phone_number : null ) . '" />
    </div>

    <div>
    <label for="subject">Subject <strong>*</strong></label>
    <input type="text" name="email_subject" value="' . ( isset( $_POST['email_subject'] ) ? $subject : null ) . '" />
    </div>

    <div>
    <label for="message">Message <strong>*</strong></label>
    <textarea name="email_message">' . ( isset( $_POST['email_message'] ) ? $message : null ) . '</textarea>
    </div>

    <div>
    <input type="submit" name="send_message" value="Send" />
    </div>
    </form>';
}

function validate_form( $name, $email, $phone_number, $subject, $message ) {

    // Make the WP_Error object global    
    global $form_error;

    // instantiate the class
    $form_error = new WP_Error;

    // If any field is left empty, add the error message to the error object
    if ( empty( $name ) || empty( $email ) || empty( $phone_number ) || empty( $subject ) || empty( $message ) ) {
        $form_error->add( 'field', 'No field should be left empty' );
    }

    // if the name field isn't alphabetic, add the error message
    if ( ! ctype_alpha( $name ) ) {
        $form_error->add( 'invalid_name', 'Invalid name entered' );
    }

    // Check if the email is valid
    if ( ! is_email( $email ) ) {
        $form_error->add( 'invalid_email', 'Email is not valid' );
    }

    // if phone number isn't numeric, throw an error
    if ( ! is_numeric( $phone_number ) ) {
        $form_error->add( 'phone_number', 'Phone-number is not numbers' );
    }

    // if $form_error is WordPress Error, loop through the error object
    // and echo the error
    if ( is_wp_error( $form_error ) ) {
        foreach ( $form_error->get_error_messages() as $error ) {
            echo '<div>';
            echo '<strong>ERROR</strong>:';
            echo $error . '<br/>';
            echo '</div>';
        }
    }

}

function send_mail( $name, $email, $phone_number, $subject, $message ) {
    global $form_error;

    // Ensure WP_Error object ($form_error) contain no error
    if ( 1 > count( $form_error->get_error_messages() ) ) {

        // sanitize user form input
        $name           =   sanitize_text_field( $name );
        $email          =   sanitize_email( $email );
        $phone_number   =   esc_attr( $phone_number );
        $subject        =   sanitize_text_field( $subject );
        $message        =   esc_textarea( $message );

        // set the variable argument use by the wp_mail
        $message    .=  '\n Phone Number:' . $phone_number;
        $to         =   'admin@tech4sky.com';
        $headers    =   "From: $name <$email>" . "\r\n";

        // If email has been process for sending, display a success message 
        if ( wp_mail( $to, $subject, $message, $headers ) ) {
            echo "Thanks for contacting me.";
        }

    }
}

function contact_form_function() {
    global $name, $email, $phone_number, $subject, $message;
    if ( isset($_POST['send_message']) ) {
        // Get the form data
        $name           =   $_POST['sender_name'];
        $email          =   $_POST['sender_email'];
        $phone_number   =   $_POST['sender_phonenumber'];
        $subject        =   $_POST['email_subject'];
        $message        =   $_POST['email_message'];

        // validate the user form input
        validate_form( $name, $email, $phone_number, $subject, $message );

        // send the mail
        send_mail( $name, $email, $phone_number, $subject, $message );

    }

    // display the contact form
    contact_html_form();

}

// Register a new shortcode: [cf_contact_form]
add_shortcode('cf_contact_form', 'contact_form_shortcode');

// Shortcode callback function
function contact_form_shortcode() {
    ob_start();
    contact_form_function();
    return ob_get_clean();
}

<?php contact_form_function(); ?>