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run code in 150+ php & hhvm versions
Bugs & Features
<?php function userland_func_get_arg($idx) { return isset(debug_backtrace()[1]['args'][$idx]) ? debug_backtrace()[1]['args'][$idx] : false; } function foo() { $a = func_get_arg(0); $a = 'bar'; } function bar() { $a = userland_func_get_arg(0); $a = 'bar'; } $foo = 'foo'; var_dump(foo($foo, 'bar')); var_dump($foo); $foo = 'foo'; var_dump(bar($foo, 'bar')); var_dump($foo);
based on FglMr
Output for 5.4.0 - 5.6.28, hhvm-3.12.0, 7.0.0 - 7.1.0
NULL string(3) "foo" NULL string(3) "foo"
Output for hhvm-3.10.0

Process exited with code 153.
Output for 5.0.0 - 5.3.29
Fatal error: Can't use function return value in write context in /in/FLgBP on line 3
Process exited with code 255.
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected T_STRING, expecting T_VARIABLE or '$' in /in/FLgBP on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.4.1
Parse error: parse error, unexpected T_STRING, expecting T_VARIABLE or '$' in /in/FLgBP on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_VARIABLE' or `'$'' in /in/FLgBP on line 3
Process exited with code 255.