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<?php $str = 'a:4:{s:20:"option_list_contents";a:3:{s:4:"type";s:6:"master";s:3:"iId";s:1:"1";s:4:"list";a:2:{i:0;a:2:{s:2:"Id";s:4:"Male";s:3:"Val";s:4:"Male";}i:1;a:2:{s:2:"Id";s:6:"Female";s:3:"Val";s:6:"Female";}}}s:4:"size";s:6:"medium";s:16:"default_required";s:3:"Yes";s:14:"field_comments";s:0:"";}'; print_r(unserialize($str));
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Array ( [option_list_contents] => Array ( [type] => master [iId] => 1 [list] => Array ( [0] => Array ( [Id] => Male [Val] => Male ) [1] => Array ( [Id] => Female [Val] => Female ) ) ) [size] => medium [default_required] => Yes [field_comments] => )

preferences:
195.65 ms | 407 KiB | 313 Q