PHP Hotel Management System Not Working? Fix Common Errors

Running into errors after installing a PHP hotel management system is common — especially with free downloads that haven't been updated in years. This covers the errors that come up most often, what causes them, and how to fix each one.

"Fatal error: Call to undefined function mysql_connect()" or similar

This is the single most common error with older, free PHP hotel booking systems. The mysql_* family of functions (mysql_connect(), mysql_query(), etc.) was deprecated in PHP 5.5 and removed entirely in PHP 7 — any hosting running PHP 7 or 8 (which is effectively all current hosting) will fatal-error immediately on code that still uses them.

Fix: the code needs to be rewritten to use mysqli_* functions or PDO instead. There's no configuration setting that restores the old functions — it's a genuine code compatibility issue, and it's exactly why checking a system's PHP version support before buying matters more than the feature list.

Two bookings for the same room on overlapping dates

Double bookings usually come down to one specific bug: checking whether a new booking's date starts on an already-booked day, instead of checking whether the date ranges overlap at all. The correct overlap check compares both ends of the range:

WHERE room_id = :room
  AND check_in  < :requested_check_out
  AND check_out > :requested_check_in

A booking that starts before the requested dates and ends inside them, or one that fully swallows the requested range, both need to be caught — a same-day-start-only check misses both. One thing this logic should NOT flag as a conflict: a same-day turnover, where one guest checks out and another checks in on the same date — that's normal occupancy, not a double booking.

Blank white page with no error message

A blank page (the "white screen of death") almost always means a PHP fatal error occurred, but display_errors is turned off on that hosting environment — common on production servers for security reasons. Check the server's PHP error log (via your hosting control panel's file manager, or ask support where it's located) rather than the browser — the actual error message is there, just not shown on-screen.

"Access denied for user" errors

This means the database username or password in the application's config/database connection file doesn't match what's actually set up on the server. Double-check both values against what your hosting control panel shows for the database — a common cause is copying config values from local development (e.g. XAMPP's default root with no password) and forgetting to update them for the live server.

Session expires immediately after logging in

If you're redirected straight back to the login page after entering correct credentials, the most common cause is a session storage misconfiguration — either the server's session save path isn't writable, or (if the system uses database-backed sessions) the sessions table doesn't exist or the session write is silently failing. Confirm the sessions table exists (if applicable) and that the hosting account's temp directory has correct write permissions.

"Table doesn't exist" errors after installation

This means the database import didn't fully complete, or the application is pointed at a different database than the one you imported into. Re-run the .sql import via phpMyAdmin and confirm all expected tables appear before testing the application again.

Booking confirmation emails not sending

This is usually a mail configuration issue rather than an application bug. Shared hosting typically requires either PHP's built-in mail() function to be enabled for the account, or SMTP credentials configured explicitly (via your hosting provider's SMTP server) — a system that worked in local development often fails silently on production because mail() isn't configured the same way. Check your host's mail sending documentation, and confirm the "from" address matches a domain you actually control (many hosts block sending as an unrelated domain).

Payment gateway works in testing but not after going live

The most frequent cause is leftover test/sandbox API keys still in the configuration after switching a payment gateway to live mode — test and live keys are separate credentials, and forgetting to swap them means transactions fail (or worse, appear to succeed without actually charging). Always do one real, small-value test transaction after switching to live keys before considering the system production-ready.

When these errors mean you need a different system, not a fix

Some of these — especially the PHP 7/8 compatibility issue — aren't five-minute fixes; they mean the codebase hasn't been maintained. If a free download consistently hits these errors, that's the real cost of "free": hours spent debugging code you didn't write, with no one to ask when you get stuck. A tested, currently-maintained codebase with support included avoids all of the above by construction.

Want a version that just works? Our Hotel Management System in PHP is tested on PHP 8, ships with the complete database, includes a commercial license for client projects, and comes with an optional installation service.