<?php
header("Content-Type: text/plain; charset=UTF-8");
echo "== WP DB-ERROR DIAG ==\n";
echo "DB_NAME=".(defined("DB_NAME")?DB_NAME:"(undef)")."\n";
echo "DB_USER=".(defined("DB_USER")?DB_USER:"(undef)")."\n";
echo "DB_HOST=".(defined("DB_HOST")?DB_HOST:"(undef)")."\n";
echo "table_prefix=".(isset($table_prefix)?$table_prefix:"(unset)")."\n";

$mysqli_loaded = extension_loaded("mysqli");
$pdo_loaded    = extension_loaded("pdo_mysql");
echo "ext.mysqli=$mysqli_loaded ext.pdo_mysql=$pdo_loaded\n";

if (!defined("DB_HOST") || !defined("DB_USER") || !defined("DB_PASSWORD") || !defined("DB_NAME")) {
  echo "DEF_ERR: DB constants not fully defined in wp-config.php\n";
  exit;
}

$lnk = @mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
if (!$lnk) {
  echo "CONNECT_ERR: ".mysqli_connect_error()."\n";
  exit;
}
$r = mysqli_query($lnk,"SELECT DATABASE() db, VERSION() ver");
$row = $r?mysqli_fetch_assoc($r):[];
echo "CONNECT_OK db=".(@$row["db"])." mysql=".(@$row["ver"])."\n";
mysqli_close($lnk);
echo "DONE\n";