Index.php hosting requires a PHP runtime. Unlike index.html, an index.php file must be executed on the server before the browser receives a page. Create the site as a PHP project, not as a static ZIP website.
Use the correct public root
For a simple project, index.php may sit at the archive root. Framework projects often use a public folder and should be prepared according to their framework documentation before deployment. Do not expose configuration files, source directories, or secrets merely to make a route work.
Use environment settings for secrets
Keep database passwords and API keys outside the ZIP. Add them in the platform environment configuration. If the site returns 500, inspect the error log for the missing file, variable, or extension instead of displaying debug output to visitors.