Online PHP editor | output for PXndP

Output for 8.3.0 - 8.3.6: Fatal error: Uncaught Error: foo(): Argument #1 could not be passed by reference in /in/PXndP:8 Stack trace: #0 {main} thrown in /in/PXndP on line 8
Process exited with code 255.
Output for 8.1.23 - 8.1.28, 8.2.10 - 8.2.18: Fatal error: Uncaught Error: foo(): Argument #1 cannot be passed by reference in /in/PXndP:8 Stack trace: #0 {main} thrown in /in/PXndP on line 8
Process exited with code 255.
Output for 5.4.0 - 5.4.32: Parse error: syntax error, unexpected '.', expecting variable (T_VARIABLE) in /in/PXndP on line 3
Process exited with code 255.
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29: Parse error: syntax error, unexpected '.', expecting T_VARIABLE in /in/PXndP on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5: Parse error: parse error, unexpected '.', expecting T_VARIABLE in /in/PXndP on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4: Parse error: parse error, expecting `T_VARIABLE' in /in/PXndP on line 3
Process exited with code 255.