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<?php function is_cyclic(array &$array) { json_encode($array); return json_last_error() === JSON_ERROR_RECURSION; } $array = [1, [2, 3]]; $array[1][1] = &$array; var_dump(is_cyclic($array));
Output for 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.17, 8.5.0 - 8.5.2
bool(true)
Output for 5.4.0 - 5.4.45
Warning: json_encode(): recursion detected in /in/3A3Eg on line 4 Notice: Use of undefined constant JSON_ERROR_RECURSION - assumed 'JSON_ERROR_RECURSION' in /in/3A3Eg on line 5 bool(false)
Output for 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/3A3Eg on line 8
Process exited with code 255.
Output for 5.0.0 - 5.0.5
Parse error: parse error, unexpected T_ARRAY, expecting '&' or T_VARIABLE in /in/3A3Eg on line 3
Process exited with code 255.
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected T_ARRAY, expecting ')' in /in/3A3Eg 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
Parse error: parse error, unexpected T_ARRAY, expecting ')' in /in/3A3Eg on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `')'' in /in/3A3Eg on line 3
Process exited with code 255.
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