3v4l.org

run code in 300+ PHP versions simultaneously
<?php class a { static $i =0; function __toString() { $a = ['', 'a']; $r = $a[$i]; $i++; return $r; } } $a = new a; var_dump('' == $a and 'a' == $a);
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Warning: Undefined variable $i in /in/Q10lr on line 7 Warning: Undefined array key "" in /in/Q10lr on line 7 Warning: Undefined variable $i in /in/Q10lr on line 8 Fatal error: Uncaught TypeError: a::__toString(): Return value must be of type string, null returned in /in/Q10lr:9 Stack trace: #0 /in/Q10lr(13): a->__toString() #1 {main} thrown in /in/Q10lr on line 9
Process exited with code 255.
Output for 7.4.0 - 7.4.33
Notice: Undefined variable: i in /in/Q10lr on line 7 Notice: Undefined index: in /in/Q10lr on line 7 Notice: Undefined variable: i in /in/Q10lr on line 8 Fatal error: Uncaught Error: Method a::__toString() must return a string value in /in/Q10lr:13 Stack trace: #0 {main} thrown in /in/Q10lr on line 13
Process exited with code 255.
Output for 7.3.32 - 7.3.33
Recoverable fatal error: Method a::__toString() must return a string value in /in/Q10lr on line 13
Process exited with code 255.
Output for 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.31
Notice: Undefined variable: i in /in/Q10lr on line 7 Notice: Undefined index: in /in/Q10lr on line 7 Notice: Undefined variable: i in /in/Q10lr on line 8 Recoverable fatal error: Method a::__toString() must return a string value in /in/Q10lr on line 13
Process exited with code 255.
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.38, 7.0.0 - 7.0.33
Notice: Undefined variable: i in /in/Q10lr on line 7 Notice: Undefined index: in /in/Q10lr on line 7 Notice: Undefined variable: i in /in/Q10lr on line 8 Catchable fatal error: Method a::__toString() must return a string value in /in/Q10lr on line 13
Process exited with code 255.

preferences:
303.86 ms | 402 KiB | 339 Q