The Extension Does Not Load

Symptom	Check and action
Cannot open shared object or module cannot be found	Confirm the absolute extension path and all companion libraries; inspect `ldd` on Linux and the required Microsoft runtime on Windows.
Wrong ELF class or not a valid Win32 application	Match the extension architecture to PHP. A 64-bit operating system alone does not identify the running PHP architecture.
Module API mismatch or undefined symbol	Use the extension for the actual PHP minor version and selected TS or NTS build (830 for PHP 8.3; 850 for PHP 8.5). Do not reuse an older extension.
PHP CLI works, APPX fails	Compare PATH, the loaded php.ini, account, current directory and filesystem permissions from the APPX execution context.
Browser demo works, APPX fails	Compare CLI PHP with web PHP. Configure the CLI's php.ini.

Inspect startup errors before changing the application chart definition. An extension that cannot load is below the APPX API layer.