Online PHP editor | output for gaT4U

Output for 8.0.0 - 8.0.12, 8.0.14 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7: Fatal error: Uncaught Error: Call to undefined function mail() in /in/gaT4U:3 Stack trace: #0 {main} thrown in /in/gaT4U on line 3
Process exited with code 255.
Output for 8.0.13: Warning: Undefined variable $user_to_follow in /in/gaT4U on line 4 Warning: Attempt to read property "email" on null in /in/gaT4U on line 4 Warning: Undefined variable $current_user in /in/gaT4U on line 6 Warning: Attempt to read property "username" on null in /in/gaT4U on line 6 Warning: mail(): Could not execute mail delivery program '/usr/sbin/sendmail -t -i' in /in/gaT4U on line 7
Output for 7.2.0 - 7.2.33, 7.3.0 - 7.3.31, 7.4.0 - 7.4.33: Notice: Undefined variable: user_to_follow in /in/gaT4U on line 4 Notice: Trying to get property 'email' of non-object in /in/gaT4U on line 4 Notice: Undefined variable: current_user in /in/gaT4U on line 6 Notice: Trying to get property 'username' of non-object in /in/gaT4U on line 6 Warning: mail() has been disabled for security reasons in /in/gaT4U on line 7
Output for 7.3.32 - 7.3.33: Warning: mail(): Could not execute mail delivery program '/usr/sbin/sendmail -t -i' in /in/gaT4U on line 7
Output for 7.0.0 - 7.0.33, 7.1.0 - 7.1.33: Notice: Undefined variable: user_to_follow in /in/gaT4U on line 4 Notice: Trying to get property of non-object in /in/gaT4U on line 4 Notice: Undefined variable: current_user in /in/gaT4U on line 6 Notice: Trying to get property of non-object in /in/gaT4U on line 6 Warning: mail() has been disabled for security reasons in /in/gaT4U on line 7
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40: Notice: Undefined variable: user_to_follow in /in/gaT4U on line 4 Notice: Trying to get property of non-object in /in/gaT4U on line 4 Notice: Undefined variable: current_user in /in/gaT4U on line 6 Notice: Trying to get property of non-object in /in/gaT4U on line 6 Warning: mail() has been disabled for security reasons in /in/gaT4U on line 8