Simplify installation when the server supports SQLite and not MySQL

src/wp-admin/setup-config.php

@@ -123,14 +123,17 @@ function setup_config_display_header( $body_classes = array() ) {
  $language = $GLOBALS['wp_local_package'];
 }
 
+$server_has_mysql = function_exists( 'mysqli_connect' ) || function_exists( 'mysql_connect' );
+$server_has_sqlite = class_exists( 'SQLite3' );
 switch ( $step ) {
  case -1:
  if ( wp_can_install_language_pack() && empty( $language ) ) {
  $languages = wp_get_available_translations();
  if ( $languages ) {
+ $action_step = ! $server_has_mysql && $server_has_sqlite ? '2' : '0';
  setup_config_display_header( 'language-chooser' );
  echo '<h1 class="screen-reader-text">Select a default language</h1>';
- echo '<form id="setup" method="post" action="?step=0">';
+ echo '<form id="setup" method="post" action="?step=' . $action_step . '">';
  wp_install_language_form( $languages );
  echo '</form>';
  break;
@@ -164,7 +167,7 @@ function setup_config_display_header( $body_classes = array() ) {
  ?>
 </h1>
 <p>
- <?php if ( class_exists( 'SQLite3' ) ) : ?>
+ <?php if ( $server_has_mysql && $server_has_sqlite ) : ?>
  <?php _e( 'Welcome to WordPress. Before getting started, you will need to know whether you want to use a MySQL (default), or an SQLite database. If you choose to use MySQL, you will need to provide the following details:' ); ?>
  <?php else : ?>
  <?php _e( 'Welcome to WordPress. Before getting started, you will need to know the following items.' ); ?>
@@ -291,17 +294,24 @@ function setup_config_display_header( $body_classes = array() ) {
  break;
 
  case 2:
+ // If the server doesn't support MySQL, we skipped steps 0 & 1.
+ if ( ! $server_has_mysql && ! empty( $language ) ) {
+ wp_download_language_pack( $language );
+ }
  load_default_textdomain( $language );
  $GLOBALS['wp_locale'] = new WP_Locale();
 
  $dbtype = trim( wp_unslash( $_POST['dbtype'] ) );
- $dbtype = class_exists( 'SQLite3' ) && 'sqlite' === $dbtype ? 'sqlite' : 'mysql';
+ $dbtype = $server_has_sqlite && 'sqlite' === $dbtype ? 'sqlite' : 'mysql';
+ $dbtype = $server_has_mysql && ! $server_has_sqlite ? 'mysql' : $dbtype;
+ $dbtype = $server_has_sqlite && ! $server_has_mysql ? 'sqlite' : $dbtype;
 
  $dbname = trim( wp_unslash( $_POST['dbname'] ) );
  $uname = trim( wp_unslash( $_POST['uname'] ) );
  $pwd = trim( wp_unslash( $_POST['pwd'] ) );
  $dbhost = trim( wp_unslash( $_POST['dbhost'] ) );
  $prefix = trim( wp_unslash( $_POST['prefix'] ) );
+ $prefix = empty( $prefix ) ? 'wp_' : $prefix;
 
  $step_1 = 'setup-config.php?step=1';
  $install = 'install.php';
@@ -545,6 +555,18 @@ function setup_config_display_header( $body_classes = array() ) {
 
 <p class="step"><a href="<?php echo $install; ?>" class="button button-large"><?php _e( 'Run the installation' ); ?></a></p>
  <?php
+ /*
+ * If the server doesn't have MySQL installed and we got this far,
+ * this is a good indication that the server is using SQLite.
+ * We can redirect to the next step, skipping the confirmation.
+ * If the user's browser doesn't support JavaScript, they will see
+ * the same confirmation page as everyone else.
+ */
+ if ( ! $server_has_mysql ) :
+ echo '<script>window.location.href = "' . $install . '";</script>';
+ endif;
+ ?>
+ <?php
  else :
  printf( '<p>%s</p>', $error_message );
  endif;