该功能主要是用于免插件为用户添加头像，解决头像无法显示或无法更换自定义头像的问题

虽热这个功能使用场景和频率都非常低，但在有时候还是需要WordPress来显示头像的，但是zuanmang.net并不是每个人都有注册设置Gravatar头像。所以便需要我们手动为WordPress添加后台可自定义上传头像的功能，如下:

将下面的代码加入到你主题的Functions.php 文件中，然后刷新页面。进入用户资料页，滑到底部，点击上传头像即可

//自定义头像

class Simple_Local_Avatars {
    private $user_id_being_edited;
        
    public function __construct() {
        add_filter( 'get_avatar', array( $this, 'get_avatar' ), 10, 5 );
        
        add_action( 'admin_init', array( $this, 'admin_init' ) );
        
        add_action( 'show_user_profile', array( $this, 'edit_user_profile' ) );
        add_action( 'edit_user_profile', array( $this, 'edit_user_profile' ) );
        
        add_action( 'personal_options_update', array( $this, 'edit_user_profile_update' ) );
        add_action( 'edit_user_profile_update', array( $this, 'edit_user_profile_update' ) );
        
        add_filter( 'avatar_defaults', array( $this, 'avatar_defaults' ) );
    }
        
    public function get_avatar( $avatar = '', $id_or_email, $size = 96, $default = '', $alt = false ) {
        
        if ( is_numeric($id_or_email) )
            $user_id = (int) $id_or_email;
        elseif ( is_string( $id_or_email ) && ( $user = get_user_by( 'email', $id_or_email ) ) )
            $user_id = $user->ID;
        elseif ( is_object( $id_or_email ) && ! empty( $id_or_email->user_id ) )
            $user_id = (int) $id_or_email->user_id;
        
        if ( empty( $user_id ) )
            return $avatar;
        
        $local_avatars = get_user_meta( $user_id, 'simple_local_avatar', true );
        
        if ( empty( $local_avatars ) || empty( $local_avatars['full'] ) )
            return $avatar;
        
        $size = (int) $size;
        
        if ( empty( $alt ) )
            $alt = get_the_author_meta( 'display_name', $user_id );
        
        // generate a new size
        if ( empty( $local_avatars[$size] ) ) {
            $upload_path = wp_upload_dir();
            $avatar_full_path = str_replace( $upload_path['baseurl'], $upload_path['basedir'], $local_avatars['full'] );
            $image_sized = image_resize( $avatar_full_path, $size, $size, true );      
            // deal with original being >= to original image (or lack of sizing ability)
            $local_avatars[$size] = is_wp_error($image_sized) ? $local_avatars[$size] = $local_avatars['full'] : str_replace( $upload_path['basedir'], $upload_path['baseurl'], $image_sized );
            // save updated avatar sizes
            update_user_meta( $user_id, 'simple_local_avatar', $local_avatars );
        } elseif ( substr( $local_avatars[$size], 0, 4 ) != 'http' ) {
            $local_avatars[$size] = home_url( $local_avatars[$size] );
        }
        
        $author_class = is_author( $user_id ) ? ' current-author' : '' ;
        $avatar = "<img alt='" . esc_attr( $alt ) . "' src='" . $local_avatars[$size] . "' class='avatar avatar-{$size}{$author_class} photo' height='{$size}' width='{$size}' />";
        
        return apply_filters( 'simple_local_avatar', $avatar );
    }
        
    public function admin_init() {
        //load_plugin_textdomain( 'simple-local-avatars', false, dirname( plugin_basename( __FILE__ ) ) . '/localization/' );
        
        register_setting( 'discussion', 'simple_local_avatars_caps', array( $this, 'sanitize_options' ) );
        add_settings_field( 'simple-local-avatars-caps', __('Local Avatar Permissions','simple-local-avatars'), array( $this, 'avatar_settings_field' ), 'discussion', 'avatars' );
    }
        
    public function sanitize_options( $input ) {
        $new_input['simple_local_avatars_caps'] = empty( $input['simple_local_avatars_caps'] ) ? 0 : 1;
        return $new_input;
    }
        
    public function avatar_settings_field( $args ) {       
        $options = get_option('simple_local_avatars_caps');
        
        echo '
            <label for="simple_local_avatars_caps">
                <input type="checkbox" name="simple_local_avatars_caps" id="simple_local_avatars_caps" value="1" ' . @checked( $options['simple_local_avatars_caps'], 1, false ) . ' />
                ' . __('仅具有头像上传权限的用户具有设置本地头像权限（作者及更高等级角色）。','simple-local-avatars') . '
            </label>
        ';
    }
        
    public function edit_user_profile( $profileuser ) {
    ?>
    <h3><?php _e( '头像','simple-local-avatars' ); ?></h3>
        
    <table class="form-table">
        <tr>
            <th><label for="simple-local-avatar"><?php _e('上传头像','simple-local-avatars'); ?></label></th>
            <td style="width: 50px;" valign="top">
                <?php echo get_avatar( $profileuser->ID ); ?>
            </td>
            <td>
            <?php
                $options = get_option('simple_local_avatars_caps');
        
                if ( empty($options['simple_local_avatars_caps']) || current_user_can('upload_files') ) {
                    do_action( 'simple_local_avatar_notices' );
                    wp_nonce_field( 'simple_local_avatar_nonce', '_simple_local_avatar_nonce', false );
            ?>
                    <input type="file" name="simple-local-avatar" id="simple-local-avatar" /><br />
            <?php
                    if ( empty( $profileuser->simple_local_avatar ) )
                        echo '<span class="description">' . __('尚未设置本地头像，请点击“浏览”按钮上传本地头像。','simple-local-avatars') . '</span>';
                    else
                        echo '
                            <input type="checkbox" name="simple-local-avatar-erase" value="1" /> ' . __('移除本地头像','simple-local-avatars') . '<br />
                            <span class="description">' . __('如需要修改本地头像，请重新上传新头像。如需要移除本地头像，请选中上方的“移除本地头像”复选框并更新个人资料即可。<br/>移除本地头像后，将恢复使用 Gravatar 头像。','simple-local-avatars') . '</span>
                        ';     
                } else {
                    if ( empty( $profileuser->simple_local_avatar ) )
                        echo '<span class="description">' . __('尚未设置本地头像，请在 Gravatar.com 网站设置头像。','simple-local-avatars') . '</span>';
                    else
                        echo '<span class="description">' . __('你没有头像上传权限，如需要修改本地头像，请联系站点管理员。','simple-local-avatars') . '</span>';
                }
            ?>
            </td>
        </tr>
    </table>
    <script type="text/javascript">var form = document.getElementById('your-profile');form.encoding = 'multipart/form-data';form.setAttribute('enctype', 'multipart/form-data');</script>
    <?php       
    }
        
    public function edit_user_profile_update( $user_id ) {
        if ( ! isset( $_POST['_simple_local_avatar_nonce'] ) || ! wp_verify_nonce( $_POST['_simple_local_avatar_nonce'], 'simple_local_avatar_nonce' ) )            //security
            return;
        
        if ( ! empty( $_FILES['simple-local-avatar']['name'] ) ) {
            $mimes = array(
                'jpg|jpeg|jpe' => 'image/jpeg',
                'gif' => 'image/gif',
                'png' => 'image/png',
                'bmp' => 'image/bmp',
                'tif|tiff' => 'image/tiff'
            );
        
            // front end (theme my profile etc) support
            if ( ! function_exists( 'wp_handle_upload' ) )
                require_once( ABSPATH . 'wp-admin/includes/file.php' );
        
            $this->avatar_delete( $user_id );    // delete old images if successful
        
            // need to be more secure since low privelege users can upload
            if ( strstr( $_FILES['simple-local-avatar']['name'], '.php' ) )
                wp_die('For security reasons, the extension ".php" cannot be in your file name.');
        
            $this->user_id_being_edited = $user_id; // make user_id known to unique_filename_callback function
            $avatar = wp_handle_upload( $_FILES['simple-local-avatar'], array( 'mimes' => $mimes, 'test_form' => false, 'unique_filename_callback' => array( $this, 'unique_filename_callback' ) ) );
        
            if ( empty($avatar['file']) ) {     // handle failures
                switch ( $avatar['error'] ) {
                    case 'File type does not meet security guidelines. Try another.' :
                        add_action( 'user_profile_update_errors', create_function('$a','$a->add("avatar_error",__("请上传有效的图片文件。","simple-local-avatars"));') );              
                        break;
                    default :
                        add_action( 'user_profile_update_errors', create_function('$a','$a->add("avatar_error","<strong>".__("上传头像过程中出现以下错误：","simple-local-avatars")."</strong> ' . esc_attr( $avatar['error'] ) . '");') );
                }
        
                return;
            }
        
            update_user_meta( $user_id, 'simple_local_avatar', array( 'full' => $avatar['url'] ) );      // save user information (overwriting old)
        } elseif ( ! empty( $_POST['simple-local-avatar-erase'] ) ) {
            $this->avatar_delete( $user_id );
        }
    }
        
    /**
     * remove the custom get_avatar hook for the default avatar list output on options-discussion.php
     */
    public function avatar_defaults( $avatar_defaults ) {
        remove_action( 'get_avatar', array( $this, 'get_avatar' ) );
        return $avatar_defaults;
    }
        
    /**
     * delete avatars based on user_id
     */
    public function avatar_delete( $user_id ) {
        $old_avatars = get_user_meta( $user_id, 'simple_local_avatar', true );
        $upload_path = wp_upload_dir();
        
        if ( is_array($old_avatars) ) {
            foreach ($old_avatars as $old_avatar ) {
                $old_avatar_path = str_replace( $upload_path['baseurl'], $upload_path['basedir'], $old_avatar );
                @unlink( $old_avatar_path );   
            }
        }
        
        delete_user_meta( $user_id, 'simple_local_avatar' );
    }
        
    public function unique_filename_callback( $dir, $name, $ext ) {
        $user = get_user_by( 'id', (int) $this->user_id_being_edited );
        $name = $base_name = sanitize_file_name( substr(md5($user->user_login),0,12) . '_avatar' );
        $number = 1;
        
        while ( file_exists( $dir . "/$name$ext" ) ) {
            $name = $base_name . '_' . $number;
            $number++;
        }
        
        return $name . $ext;
    }
}
        
$simple_local_avatars = new Simple_Local_Avatars;
        
function get_simple_local_avatar( $id_or_email, $size = '96', $default = '', $alt = false ) {
    global $simple_local_avatars;
    $avatar = $simple_local_avatars->get_avatar( '', $id_or_email, $size, $default, $alt );
        
    if ( empty ( $avatar ) )
        $avatar = get_avatar( $id_or_email, $size, $default, $alt );
        
    return $avatar;
}
//自定义头像 结束