使用PHP读写JSON

Question

So currently I'm working on a project that requires the use of PHP and JSON. The way I have currently set up my code is so that I read the JSON file in using file_get_contents and then use the built in json_decode() function. Everything is reading perfectly, it's the writing part that is giving me trouble.

The way I have my JSON tree set up is:

{
"test":[
        {
        "testName":"Winter 2011",
        "testDate":"12/04/2011",
        "testTime":"2:00pm",
        "testRoom":"room",
        "cap": 10,
        "spotsLeft": 0,
        "student":[
            {
                "fname":"Bob",
                "lname":"Roberts",
                "usrnm":"bobr",
                "email":"bob@gmail.com"
            }
        ]
    }
]
}

To get the right test (since there will be multiple tests) I'm using a foreach loop and then I make sure there isn't a duplicate. At this point I'm ready to add a new student to the JSON file so I call: `

$file = file_get_contents('testDates.json');
$json = json_decode($file, true);

//Go through each test in the file
foreach ($json[test] as $t){
   .....
   //Works if I only do $t[student] but that only adds it to the $t[] and not the
   //JSON file. Can't seem to get it to add to the whole JSON string.
   array_push($json[$t][student], $newStudent);
   echo json_encode($json);
   .....
   //Use a file_put_contents later to write the file out

Any thoughts would be extremely helpful. It's probably a pointer error to a certain point int he array but a second set of eyes never hurt. Thanks.

Answer 1

$t is a copy, it is not referencing original object. This appens with every foreach cycle. Use instead:

foreach ($json[test] as $k => $t){
    array_push($json[test][$k][student], $newStudent);
    ...
}

Or you can try:

foreach ($json[test] as &$t){
    array_push($t[student], $newStudent);
    ...
}

See here to learn how foreach works: http://php.net/manual/en/control-structures.foreach.php

Answer 2

You're using wrong $json[$t] inside foreach instead of $json["test"][$t] and also you need to use key-value pairs

$testVal = $json["test"];
foreach ($testVal as $key => $val){
    . . .
    array_push($testVal[$key]["student"], $newStudent);
    . . .
}

PS use $json['test'] instead of $json[test], the first one causes syntax warning which PHP interprets as string "test" (in your case it's working:) )

Answer 3

Try this:

$json = json_decode($jsonString);

if($json["color"] == "blue"){
 ...
}

$json["language"] = "php";

$newJsonString = json_encode($json);

Isn't that easy?