我在JSON字符串中包含以下代码
$string={"status":1,"result":{"contest":[{"id":990173,"challenge_id":990173,"name":"","entryfee":39,"winning_amount":"0","win_amount":10000,"maximum_user":369,"getjoinedpercentage":20,"winners":0,"userid":0,"userrank":0,"team_id":0,"join_id":0,"matchkey":"43287","joinedusers":73,"team1display":"","team2display":"","multi_entry":1,"confirmed_challenge":1,"is_running":1,"is_bonus":1,"bonus_percent":"10%","isselected":false,"isselectedid":"","joinedleagueskey":13,"points":0,"isjoined":false,"join_with":0,"totalwinners":10},{"id":990172,"challenge_id":990172,"name":"","entryfee":39,"winning_amount":"0","win_amount":3000,"maximum_user":111,"getjoinedpercentage":8,"winners":0,"userid":0,"userrank":0,"team_id":0,"join_id":0,"matchkey":"43287","joinedusers":9,"team1display":"","team2display":"","multi_entry":1,"confirmed_challenge":1,"is_running":1,"is_bonus":1,"bonus_percent":"10%","isselected":false,"isselectedid":"","joinedleagueskey":1,"points":0,"isjoined":false,"join_with":0,"totalwinners":8},{"id":990043,"challenge_id":990043,"name":"","entryfee":0,"winning_amount":"0","win_amount":0,"maximum_user":100,"getjoinedpercentage":19,"winners":0,"userid":0,"userrank":0,"team_id":0,"join_id":0,"matchkey":"43287","joinedusers":19,"team1display":"","team2display":"","multi_entry":1,"confirmed_challenge":1,"is_running":1,"is_bonus":0,"bonus_percent":"0%","isselected":false,"isselectedid":"","joinedleagueskey":5,"points":0,"isjoined":false,"join_with":0,"totalwinners":0}],"user_teams":6,"joined_leagues":3}}
我需要获取最后一个字符串的challenge_id值
即：
{"id":990043,"challenge_id":990043,"name":"","entryfee":0,"winning_amount":"0","win_amount":0,"maximum_user":100,"getjoinedpercentage":19,"winners":0,"userid":0,"userrank":0,"team_id":0,"join_id":0,"matchkey":"43287","joinedusers":19,"team1display":"","team2display":"","multi_entry":1,"confirmed_challenge":1,"is_running":1,"is_bonus":0,"bonus_percent":"0%","isselected":false,"isselectedid":"","joinedleagueskey":5,"points":0,"isjoined":false,"join_with":0,"totalwinners":0}
我尝试使用preg_match来获取值：
preg_match('#"challenge_id":(.*?),"name":"","entryfee":0,"winning_amount":"0","win_amount"#',$stringg,$match);
$cid=$match[1];
我想获取值990043，但我要获取值990173，它是第一个字符串中的值。