gistfile1.php

/**
 * Class for adding a new field to the options-general.php page
 */
class ct_drop_add_profile_image_upload {

    /**
     * Class constructor
     */
    public function __construct() {
        add_filter( 'admin_init' , array( &$this , 'register_fields' ) );
    }

    /**
     * Add new fields to wp-admin/options-general.php page
     */
    public function register_fields() {
        register_setting( 'general', 'ct_drop_profile_image_upload', 'esc_attr' );
        add_settings_field(
            'ct_drop_profile_image_upload',
            '<label for="ct_drop_profile_image_upload">' . __( 'Avatar' , 'drop' ) . '</label>',
            array( &$this, 'fields_html' ),
            'general'
        );
    }

    /**
     * HTML for extra settings
     */
    public function fields_html() {
        $value = get_option( 'ct_drop_profile_image_upload', '' );

        ?>
        <!-- Outputs the image after save -->
        <img id="image-preview" src="<?php echo esc_url( $value ); ?>" style="width:100px;"><br />
        <!-- Outputs the text field and displays the URL of the image retrieved by the media uploader -->
        <input type="text" name="ct_drop_profile_image_upload" id="ct_drop_profile_image_upload" value="<?php echo esc_url_raw( $value ); ?>" class="regular-text" />
        <!-- Outputs the save button -->
        <input type='button' id="profile-image-upload" class="button-primary" value="<?php _e( 'Upload Image', 'drop' ); ?>"/><br />
        <span class="description"><?php _e( 'This image will be used in the sidebar instead of your Gravatar.', 'drop' ); ?></span>
        <?php
    }
}
new ct_drop_add_profile_image_upload();