network_step1() WordPress Function

function network_step1( $errors = false ) {
	global $is_apache;

	if ( defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
		echo '<div class="error"><p><strong>' . __( 'Error:' ) . '</strong> ' . sprintf(
			/* translators: %s: DO_NOT_UPGRADE_GLOBAL_TABLES */
			__( 'The constant %s cannot be defined when creating a network.' ),
			'<code>DO_NOT_UPGRADE_GLOBAL_TABLES</code>'
		) . '</p></div>';
		echo '</div>';
		require_once ABSPATH . 'wp-admin/admin-footer.php';
		die();
	}

	$active_plugins = get_option( 'active_plugins' );
	if ( ! empty( $active_plugins ) ) {
		echo '<div class="notice notice-warning"><p><strong>' . __( 'Warning:' ) . '</strong> ' . sprintf(
			/* translators: %s: URL to Plugins screen. */
			__( 'Please <a href="%s">deactivate your plugins</a> before enabling the Network feature.' ),
			admin_url( 'plugins.php?plugin_status=active' )
		) . '</p></div>';
		echo '<p>' . __( 'Once the network is created, you may reactivate your plugins.' ) . '</p>';
		echo '</div>';
		require_once ABSPATH . 'wp-admin/admin-footer.php';
		die();
	}

	$hostname  = get_clean_basedomain();
	$has_ports = strstr( $hostname, ':' );
	if ( ( false !== $has_ports && ! in_array( $has_ports, array( ':80', ':443' ), true ) ) ) {
		echo '<div class="error"><p><strong>' . __( 'Error:' ) . '</strong> ' . __( 'You cannot install a network of sites with your server address.' ) . '</p></div>';
		echo '<p>' . sprintf(
			/* translators: %s: Port number. */
			__( 'You cannot use port numbers such as %s.' ),
			'<code>' . $has_ports . '</code>'
		) . '</p>';
		echo '<a href="' . esc_url( admin_url() ) . '">' . __( 'Go to Dashboard' ) . '</a>';
		echo '</div>';
		require_once ABSPATH . 'wp-admin/admin-footer.php';
		die();
	}

	echo '<form method="post">';

	wp_nonce_field( 'install-network-1' );

	$error_codes = array();
	if ( is_wp_error( $errors ) ) {
		echo '<div class="error"><p><strong>' . __( 'Error: The network could not be created.' ) . '</strong></p>';
		foreach ( $errors->get_error_messages() as $error ) {
			echo "<p>$error</p>";
		}
		echo '</div>';
		$error_codes = $errors->get_error_codes();
	}

	if ( ! empty( $_POST['sitename'] ) && ! in_array( 'empty_sitename', $error_codes, true ) ) {
		$site_name = $_POST['sitename'];
	} else {
		/* translators: %s: Default network title. */
		$site_name = sprintf( __( '%s Sites' ), get_option( 'blogname' ) );
	}

	if ( ! empty( $_POST['email'] ) && ! in_array( 'invalid_email', $error_codes, true ) ) {
		$admin_email = $_POST['email'];
	} else {
		$admin_email = get_option( 'admin_email' );
	}
	?>
	<p><?php _e( 'Welcome to the Network installation process!' ); ?></p>
	<p><?php _e( 'Fill in the information below and you&#8217;ll be on your way to creating a network of WordPress sites. Configuration files will be created in the next step.' ); ?></p>
	<?php

	if ( isset( $_POST['subdomain_install'] ) ) {
		$subdomain_install = (bool) $_POST['subdomain_install'];
	} elseif ( apache_mod_loaded( 'mod_rewrite' ) ) { // Assume nothing.
		$subdomain_install = true;
	} elseif ( ! allow_subdirectory_install() ) {
		$subdomain_install = true;
	} else {
		$subdomain_install = false;
		$got_mod_rewrite   = got_mod_rewrite();
		if ( $got_mod_rewrite ) { // Dangerous assumptions.
			echo '<div class="updated inline"><p><strong>' . __( 'Note:' ) . '</strong> ';
			printf(
				/* translators: %s: mod_rewrite */
				__( 'Please make sure the Apache %s module is installed as it will be used at the end of this installation.' ),
				'<code>mod_rewrite</code>'
			);
			echo '</p>';
		} elseif ( $is_apache ) {
			echo '<div class="error inline"><p><strong>' . __( 'Warning:' ) . '</strong> ';
			printf(
				/* translators: %s: mod_rewrite */
				__( 'It looks like the Apache %s module is not installed.' ),
				'<code>mod_rewrite</code>'
			);
			echo '</p>';
		}

		if ( $got_mod_rewrite || $is_apache ) { // Protect against mod_rewrite mimicry (but ! Apache).
			echo '<p>';
			printf(
				/* translators: 1: mod_rewrite, 2: mod_rewrite documentation URL, 3: Google search for mod_rewrite. */
				__( 'If %1$s is disabled, ask your administrator to enable that module, or look at the <a href="%2$s">Apache documentation</a> or <a href="%3$s">elsewhere</a> for help setting it up.' ),
				'<code>mod_rewrite</code>',
				'https://httpd.apache.org/docs/mod/mod_rewrite.html',
				'https://www.google.com/search?q=apache+mod_rewrite'
			);
			echo '</p></div>';
		}
	}

	if ( allow_subdomain_install() && allow_subdirectory_install() ) :
		?>
		<h3><?php esc_html_e( 'Addresses of Sites in your Network' ); ?></h3>
		<p><?php _e( 'Please choose whether you would like sites in your WordPress network to use sub-domains or sub-directories.' ); ?>
			<strong><?php _e( 'You cannot change this later.' ); ?></strong></p>
		<p><?php _e( 'You will need a wildcard DNS record if you are going to use the virtual host (sub-domain) functionality.' ); ?></p>
		<?php // @todo Link to an MS readme? ?>
		<table class="form-table" role="presentation">
			<tr>
				<th><label><input type="radio" name="subdomain_install" value="1"<?php checked( $subdomain_install ); ?> /> <?php _e( 'Sub-domains' ); ?></label></th>
				<td>
				<?php
				printf(
					/* translators: 1: Host name. */
					_x( 'like <code>site1.%1$s</code> and <code>site2.%1$s</code>', 'subdomain examples' ),
					$hostname
				);
				?>
				</td>
			</tr>
			<tr>
				<th><label><input type="radio" name="subdomain_install" value="0"<?php checked( ! $subdomain_install ); ?> /> <?php _e( 'Sub-directories' ); ?></label></th>
				<td>
				<?php
				printf(
					/* translators: 1: Host name. */
					_x( 'like <code>%1$s/site1</code> and <code>%1$s/site2</code>', 'subdirectory examples' ),
					$hostname
				);
				?>
				</td>
			</tr>
		</table>

		<?php
	endif;

	if ( WP_CONTENT_DIR !== ABSPATH . 'wp-content' && ( allow_subdirectory_install() || ! allow_subdomain_install() ) ) {
		echo '<div class="error inline"><p><strong>' . __( 'Warning:' ) . '</strong> ' . __( 'Subdirectory networks may not be fully compatible with custom wp-content directories.' ) . '</p></div>';
	}

	$is_www = ( 0 === strpos( $hostname, 'www.' ) );
	if ( $is_www ) :
		?>
		<h3><?php esc_html_e( 'Server Address' ); ?></h3>
		<p>
		<?php
		printf(
			/* translators: 1: Site URL, 2: Host name, 3: www. */
			__( 'You should consider changing your site domain to %1$s before enabling the network feature. It will still be possible to visit your site using the %3$s prefix with an address like %2$s but any links will not have the %3$s prefix.' ),
			'<code>' . substr( $hostname, 4 ) . '</code>',
			'<code>' . $hostname . '</code>',
			'<code>www</code>'
		);
		?>
		</p>
		<table class="form-table" role="presentation">
			<tr>
			<th scope='row'><?php esc_html_e( 'Server Address' ); ?></th>
			<td>
				<?php
					printf(
						/* translators: %s: Host name. */
						__( 'The internet address of your network will be %s.' ),
						'<code>' . $hostname . '</code>'
					);
				?>
				</td>
			</tr>
		</table>
		<?php endif; ?>

		<h3><?php esc_html_e( 'Network Details' ); ?></h3>
		<table class="form-table" role="presentation">
		<?php if ( 'localhost' === $hostname ) : ?>
			<tr>
				<th scope="row"><?php esc_html_e( 'Sub-directory Installation' ); ?></th>
				<td>
				<?php
					printf(
						/* translators: 1: localhost, 2: localhost.localdomain */
						__( 'Because you are using %1$s, the sites in your WordPress network must use sub-directories. Consider using %2$s if you wish to use sub-domains.' ),
						'<code>localhost</code>',
						'<code>localhost.localdomain</code>'
					);
					// Uh oh:
				if ( ! allow_subdirectory_install() ) {
					echo ' <strong>' . __( 'Warning:' ) . ' ' . __( 'The main site in a sub-directory installation will need to use a modified permalink structure, potentially breaking existing links.' ) . '</strong>';
				}
				?>
				</td>
			</tr>
		<?php elseif ( ! allow_subdomain_install() ) : ?>
			<tr>
				<th scope="row"><?php esc_html_e( 'Sub-directory Installation' ); ?></th>
				<td>
				<?php
					_e( 'Because your installation is in a directory, the sites in your WordPress network must use sub-directories.' );
					// Uh oh:
				if ( ! allow_subdirectory_install() ) {
					echo ' <strong>' . __( 'Warning:' ) . ' ' . __( 'The main site in a sub-directory installation will need to use a modified permalink structure, potentially breaking existing links.' ) . '</strong>';
				}
				?>
				</td>
			</tr>
		<?php elseif ( ! allow_subdirectory_install() ) : ?>
			<tr>
				<th scope="row"><?php esc_html_e( 'Sub-domain Installation' ); ?></th>
				<td>
				<?php
				_e( 'Because your installation is not new, the sites in your WordPress network must use sub-domains.' );
					echo ' <strong>' . __( 'The main site in a sub-directory installation will need to use a modified permalink structure, potentially breaking existing links.' ) . '</strong>';
				?>
				</td>
			</tr>
		<?php endif; ?>
		<?php if ( ! $is_www ) : ?>
			<tr>
				<th scope='row'><?php esc_html_e( 'Server Address' ); ?></th>
				<td>
					<?php
					printf(
						/* translators: %s: Host name. */
						__( 'The internet address of your network will be %s.' ),
						'<code>' . $hostname . '</code>'
					);
					?>
				</td>
			</tr>
		<?php endif; ?>
			<tr>
				<th scope='row'><label for="sitename"><?php esc_html_e( 'Network Title' ); ?></label></th>
				<td>
					<input name='sitename' id='sitename' type='text' size='45' value='<?php echo esc_attr( $site_name ); ?>' />
					<p class="description">
						<?php _e( 'What would you like to call your network?' ); ?>
					</p>
				</td>
			</tr>
			<tr>
				<th scope='row'><label for="email"><?php esc_html_e( 'Network Admin Email' ); ?></label></th>
				<td>
					<input name='email' id='email' type='text' size='45' value='<?php echo esc_attr( $admin_email ); ?>' />
					<p class="description">
						<?php _e( 'Your email address.' ); ?>
					</p>
				</td>
			</tr>
		</table>
		<?php submit_button( __( 'Install' ), 'primary', 'submit' ); ?>
	</form>
	<?php
}