The function `json_decode()` can be used to convert JSON data to PHP variables. Arrays as well as objects can be converted to their equivalent PHP literals.
Here are some examples :
JSON Arrays
// Hello World $json = '["Hello","World"]'; $array = json_decode($json); echo($array[0]); // Hello
$json = [ 100, 500, 300, 200, 400 ] ; $array = json_decode($json); echo($array[3]); // 200 echo($array[1]); // 500
JSON Objects
JSON objects are converted to PHP objects by default
$jsonObject = '{
"Name":"John",
"Surname":"Doe"
}';
$obj = json_decode($jsonObject);
echo($obj->Surname); // Doe
The function `json_decode()` provides an optional boolean second-argument that if passed as `true` converts objects into PHP associative arrays. Using the example from above, and decoding it as such, the elements can be accessed using the respective keys.
$jsonObject = '{
"Name":"John",
"Surname":"Doe"
}';
$assocArray = json_decode($jsonObject, true);
// Accessing elements using standard array syntax
echo($assocArray['Name']); // John
Handling Multi-dimensional Objects
`json_decode()` can recursively decode JSON strings. The third optional argument tells the function the depth to which decoding should happen.
Consider a JSON string that represents an indexed array of objects.
$json = '[ {"id":"1", "name":"foo" }, {"id":"2", "name":"bar" } ]';
$baz = json_decode($json);
echo($baz[0]->name); // foo
If true were to be passed as the second argument to `json_decode()` above, one would end up with a numerically indexed array of associative arrays.
$json = '[ {"id":"1", "name":"foo" }, {"id":"2", "name":"bar" } ]';
$baz = json_decode($json,true);
echo($baz[1]['name']); //bar
Iterating over Multidimensional arrays
Consider a JSON string that when decoded results in a multidimensional PHP literal. Such a literal can be efficiently iterated over using a `RecursiveIteratorIterator`.
$json = '{ "John":{ "gender":"male", "age":"12" }, "Jen":{ "gender":"female", "age":"13" } }';
$iter = new RecursiveIteratorIterator( new RecursiveArrayIterator(jsondecode($json,true)), RecursiveIteratorIterator::SELFFIRST);
foreach($iter as $key=>$value) {
if(is_array($value))
{ echo "$key:\n"; }
else
{ echo "$key => $value\n"; }
}
/*
The output will be :
John:
gender => male
age => 12
Jen:
gender => female
age => 13
*/
Handling Errors
`json_decode()` returns `NULL` if the JSON string cannot be decoded or the encoded data is deeper than the recursion limit. In such cases, the functions `json_last_error()` and `json_last_error_msg()` provide useful information.
$json = '["1"2]'; $var = json_decode($json); var_dump($var); // NULL echo json_last_error(); // 4 echo json_last_error_msg(); // Syntax error
