parsing JSON data with PHP....large dataset - php

Question

below is the dataset I am trying to parse and put into db... I am using this code
$json = json_decode($string);
$json[0]['segments']['layover'] gives access error...
also sizeof($json) returns nothing...
$json doesn't return null,is checked, prints with echo var_dump($json)
I have attempted to foreach through this...doesn't work.. tried an array type and is saying that I am illegal access stdIN object...is there anything as easy as DOMDocument() to walk through json?
---json
[{"legs":[{"segments":[{"layover":{"hours":1,"minutes":28},"totalTravelingTime":{"hours":1,"minutes":10},"departureAirport":{"airportCode":"ABE","airportCity":"Allentown","airportName":"Allentown (ABE)","airportCityState":"Allentown, PA"},"arrivalAirport":{"airportCode":"IAD","airportCity":"Washington","airportName":"Washington (IAD)","airportCityState":"Washington, DC"},"departureDate":1328811900000,"arrivalDate":1328816100000,"flightNumber":"3866","elapsedNumberOfDays":0,"departureDateTime":{"month":2,"year":2012,"timeZone":"GMT-05:00","day":9,"second":0,"minute":25,"hour":10,"milliSecond":0,"xsdTimeType":"DATETIME_WITH_TIMEZONE","dateTimeString":"2012-02-09T10:25:00-05:00"},"segmentLegSequenceIndex":1,"airCarrierCode":"UA","aircraftType":"Saab 340/340B","aircraftCode":"SF3","airline":{"activeState":"ACTIVE","airlineCode":"UA","airlineName":"UNITED","majorAirline":true,"imageFilename":"UA.gif","preferredAirline":false},"bookingCode":"S","cabinClass":"3","seatMapAvailable":true,"segmentSequenceIndex":1,"formattedDepartureTime":"10:25am","formattedArrivalTime":"11:35am","operatedBy":"/UNITED EXPRESS/COLGAN AIR","formattedDepartureDate":"2/9/12","formattedArrivalDate":"2/9/12","operatingAirlineCode":"","wiFiAvailable":false},{"layover":{"hours":1,"minutes":5},"totalTravelingTime":{"hours":3,"minutes":27},"departureAirport":{"airportCode":"IAD","airportCity":"Washington","airportName":"Washington (IAD)","airportCityState":"Washington, DC"},"arrivalAirport":{"airportCode":"DFW","airportCity":"Dallas","airportName":"Dallas (Dallas-Fort Worth Intl.)","airportCityState":"Dallas, TX"},"departureDate":1328821380000,"arrivalDate":1328830200000,"flightNumber":"3801","elapsedNumberOfDays":0,"departureDateTime":{"month":2,"year":2012,"timeZone":"GMT-05:00","day":9,"second":0,"minute":3,"hour":13,"milliSecond":0,"xsdTimeType":"DATETIME_WITH_TIMEZONE","dateTimeString":"2012-02-09T13:03:00-05:00"},"segmentLegSequenceIndex":1,"airCarrierCode":"UA","aircraftType":"Canadian Regional Jet 700","aircraftCode":"CR7","airline":{"activeState":"ACTIVE","airlineCode":"UA","airlineName":"UNITED","majorAirline":true,"imageFilename":"UA.gif","preferredAirline":false},"bookingCode":"S","cabinClass":"3","seatMapAvailable":true,"segmentSequenceIndex":2,"formattedDepartureTime":"1:03pm","formattedArrivalTime":"3:30pm","operatedBy":"/UNITED EXPRESS/MESA AIRLINES","formattedDepartureDate":"2/9/12","formattedArrivalDate":"2/9/12","operatingAirlineCode":"","wiFiAvailable":false},{"totalTravelingTime":{"hours":0,"minutes":50},"departureAirport":{"airportCode":"DFW","airportCity":"Dallas","airportName":"Dallas (Dallas-Fort Worth Intl.)","airportCityState":"Dallas, TX"},"arrivalAirport":{"airportCode":"ABI","airportCity":"Abilene","airportName":"Abilene (ABI)","airportCityState":"Abilene, TX"},"departureDate":1328834100000,"arrivalDate":1328837100000,"flightNumber":"2975","elapsedNumberOfDays":0,"departureDateTime":{"month":2,"year":2012,"timeZone":"GMT-06:00","day":9,"second":0,"minute":35,"hour":16,"milliSecond":0,"xsdTimeType":"DATETIME_WITH_TIMEZONE","dateTimeString":"2012-02-09T16:35:00-06:00"},"segmentLegSequenceIndex":1,"airCarrierCode":"AA","aircraftType":"Embraer RJ145","aircraftCode":"ER4","airline":{"activeState":"ACTIVE","airlineCode":"AA","airlineName":"American Airlines","majorAirline":true,"imageFilename":"AA.gif","preferredAirline":false},"bookingCode":"L","cabinClass":"3","seatMapAvailable":true,"segmentSequenceIndex":3,"formattedDepartureTime":"4:35pm","formattedArrivalTime":"5:25pm","operatedBy":"/AMERICAN EAGLE","formattedDepartureDate":"2/9/12","formattedArrivalDate":"2/9/12","operatingAirlineCode":"","wiFiAvailable":false}],"carriers":["UA","UA","AA"],"departureDateTime":{"month":2,"year":2012,"timeZone":"GMT-05:00","day":9,"second":0,"minute":25,"hour":10,"milliSecond":0,"xsdTimeType":"DATETIME_WITH_TIMEZONE","dateTimeString":"2012-02-09T10:25:00-05:00"},"arrivalDateTime":{"month":2,"year":2012,"timeZone":"GMT-06:00","day":9,"second":0,"minute":25,"hour":17,"milliSecond":0,"xsdTimeType":"DATETIME_WITH_TIMEZONE","dateTimeString":"2012-02-09T17:25:00-06:00"},"airLineImageFilePath":"","elapsedDays":0,"departureTime":"2012/02/09 10:25:00 PST","arrivalTime":"2012/02/09 17:25:00 PST","departureDate":1328811900000,"arrivalDate":1328837100000,"arrivalAirport":{"airportCode":"ABI","airportCity":"Abilene","airportName":"Abilene (ABI)","airportCityState":"Abilene, TX"},"legSequenceIndex":1,"departureAirport":{"airportCode":"ABE","airportCity":"Allentown","airportName":"Allentown (ABE)","airportCityState":"Allentown, PA"},"departureDateFormat":"2012/02/09","arrivalDateFormat":"Feb. 9","formattedDepartureTime":"10:25am","formattedArrivalTime":"5:25pm","hasTrainLeg":false,"stops":2,"totalTravelingHours":{"hours":8,"minutes":0},"formattedMiles":"1,495","hasBusLeg":false,"formattedDepartureDate":"2/9/12","formattedDepartureDateTime":"2/9/12","departureDateFormat1":"Thu. 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...so on

Answer 1

json_decode takes a second parameter to return data as an associative array instead of objects. This will solve your problem.
$json_array = json_decode($string,true); // returns 'normal' php array.
$json = json_decode($string); // returns php object hierarchy

Answer 2

http://json.parser.online.fr/ reports that you data ends unexpectedly. Do you actually have the real data? Or if is it wrong, how did you generate it? There might be errors in the generation script cause it is not complete...
There seems to be a misplaced character at the end. Instead of a comma ",", it should be a closing array "]"

Answer 3

You did not say WHY json_decode isn't working. If the JSON is too big to post here just use pastebin or something alike.
I assume the reason it's not working is because you are exceeding the memory allowance for PHP, you can work around this by increasing the max memory PHP can use, eg:
ini_set('memory_limit','16M');
However I wouldn't recommend doing this if this code is going to be ran by a large amount of users. Maybe if you give us some context we can give you an alternative solution which bypasses the need of json_decode.