WordPress/wp-admin/network/user-new.php

<?php
/**
 * Add New User network administration panel.
 *
 * @package WordPress
 * @subpackage Multisite
 * @since 3.1.0
 */

/** Load WordPress Administration Bootstrap */
require_once __DIR__ . '/admin.php';

if ( ! current_user_can( 'create_users' ) ) {
	wp_die( __( 'Sorry, you are not allowed to add users to this network.' ) );
}

get_current_screen()->add_help_tab(
	array(
		'id'      => 'overview',
		'title'   => __( 'Overview' ),
		'content' =>
			'<p>' . __( 'Add User will set up a new user account on the network and send that person an email with username and password.' ) . '</p>' .
			'<p>' . __( 'Users who are signed up to the network without a site are added as subscribers to the main or primary dashboard site, giving them profile pages to manage their accounts. These users will only see Dashboard and My Sites in the main navigation until a site is created for them.' ) . '</p>',
	)
);

get_current_screen()->set_help_sidebar(
	'<p><strong>' . __( 'For more information:' ) . '</strong></p>' .
	'<p>' . __( '<a href="https://codex.wordpress.org/Network_Admin_Users_Screen">Documentation on Network Users</a>' ) . '</p>' .
	'<p>' . __( '<a href="https://wordpress.org/support/forum/multisite/">Support forums</a>' ) . '</p>'
);

if ( isset( $_REQUEST['action'] ) && 'add-user' === $_REQUEST['action'] ) {
	check_admin_referer( 'add-user', '_wpnonce_add-user' );

	if ( ! current_user_can( 'manage_network_users' ) ) {
		wp_die( __( 'Sorry, you are not allowed to access this page.' ), 403 );
	}

	if ( ! is_array( $_POST['user'] ) ) {
		wp_die( __( 'Cannot create an empty user.' ) );
	}

	$user = wp_unslash( $_POST['user'] );

	$user_details = wpmu_validate_user_signup( $user['username'], $user['email'] );

	if ( is_wp_error( $user_details['errors'] ) && $user_details['errors']->has_errors() ) {
		$add_user_errors = $user_details['errors'];
	} else {
		$password = wp_generate_password( 12, false );
		$user_id  = wpmu_create_user( esc_html( strtolower( $user['username'] ) ), $password, sanitize_email( $user['email'] ) );

		if ( ! $user_id ) {
			$add_user_errors = new WP_Error( 'add_user_fail', __( 'Cannot add user.' ) );
		} else {
			/**
			 * Fires after a new user has been created via the network user-new.php page.
			 *
			 * @since 4.4.0
			 *
			 * @param int $user_id ID of the newly created user.
			 */
			do_action( 'network_user_new_created_user', $user_id );

			wp_redirect(
				add_query_arg(
					array(
						'update'  => 'added',
						'user_id' => $user_id,
					),
					'user-new.php'
				)
			);
			exit;
		}
	}
}

$message = '';
if ( isset( $_GET['update'] ) ) {
	if ( 'added' === $_GET['update'] ) {
		$edit_link = '';
		if ( isset( $_GET['user_id'] ) ) {
			$user_id_new = absint( $_GET['user_id'] );
			if ( $user_id_new ) {
				$edit_link = esc_url( add_query_arg( 'wp_http_referer', urlencode( wp_unslash( $_SERVER['REQUEST_URI'] ) ), get_edit_user_link( $user_id_new ) ) );
			}
		}

		$message = __( 'User added.' );

		if ( $edit_link ) {
			$message .= sprintf( ' <a href="%s">%s</a>', $edit_link, __( 'Edit user' ) );
		}
	}
}

// Used in the HTML title tag.
$title       = __( 'Add New User' );
$parent_file = 'users.php';

require_once ABSPATH . 'wp-admin/admin-header.php';
?>

<div class="wrap">
<h1 id="add-new-user"><?php _e( 'Add New User' ); ?></h1>
<?php
if ( '' !== $message ) {
	echo '<div id="message" class="notice notice-success is-dismissible"><p>' . $message . '</p></div>';
}

if ( isset( $add_user_errors ) && is_wp_error( $add_user_errors ) ) {
	?>
	<div id="message" class="notice notice-error is-dismissible">
		<?php
		foreach ( $add_user_errors->get_error_messages() as $error ) {
			echo "<p>$error</p>";
		}
		?>
	</div>
<?php } ?>
	<form action="<?php echo esc_url( network_admin_url( 'user-new.php?action=add-user' ) ); ?>" id="adduser" method="post" novalidate="novalidate">
		<p><?php echo wp_required_field_message(); ?></p>
		<table class="form-table" role="presentation">
			<tr class="form-field form-required">
				<th scope="row"><label for="username"><?php _e( 'Username' ); ?> <?php echo wp_required_field_indicator(); ?></label></th>
				<td><input type="text" class="regular-text" name="user[username]" id="username" autocapitalize="none" autocorrect="off" maxlength="60" required="required" /></td>
			</tr>
			<tr class="form-field form-required">
				<th scope="row"><label for="email"><?php _e( 'Email' ); ?> <?php echo wp_required_field_indicator(); ?></label></th>
				<td><input type="email" class="regular-text" name="user[email]" id="email" required="required" /></td>
			</tr>
			<tr class="form-field">
				<td colspan="2" class="td-full"><?php _e( 'A password reset link will be sent to the user via email.' ); ?></td>
			</tr>
		</table>
	<?php
	/**
	 * Fires at the end of the new user form in network admin.
	 *
	 * @since 4.5.0
	 */
	do_action( 'network_user_new_form' );

	wp_nonce_field( 'add-user', '_wpnonce_add-user' );
	submit_button( __( 'Add User' ), 'primary', 'add-user' );
	?>
	</form>
</div>
<?php
require_once ABSPATH . 'wp-admin/admin-footer.php';