How to Efficiently Extract and Access Data from JSON Files Using PHP?

How to extract and access data from JSON with PHP?

Json_decode() is the built-in PHP function to decode JSON.

Decoding JSON

$data = json_decode($json);

DataTypes
Decoded JSON can contain:

• Scalars: Strings, Integers, Floats, Booleans
• Nulls
• Compound types: Objects and Arrays

Object Properties
Access object properties with -> operator:

echo $object->property;

Array Elements
Access array elements with [] operator:

echo $array[0];

Nested Items
Access nested items by chaining dot or array operators:

echo $object->array[0]->etc;

Associative Arrays
Passing true as the second argument of json_decode() creates associative arrays:

echo $array['key'];

Iterating Associative Arrays
Use foreach loop to iterate over both keys and values:

foreach ($assoc as $key => $value) {
    echo "Key: $key, Value: $value";
}

Unknown Data Structure

• Consult JSON source documentation
• Examine JSON using curly brackets {} for objects and square brackets [] for arrays
• Use print_r() function to display and analyze the data

json_decode() Returns Null

• Null JSON value
• Invalid JSON (check with json_last_error_msg)
• Data depth exceeds 512 levels (override with third argument in json_decode())

Special Characters in Object Properties
Use curly braces with string literals to access properties with special characters:

echo $thing->{'@attributes'}->answer;

JSON within JSON
Decode the outer JSON and the inner JSON string to access the data:

echo json_decode(json_decode($yummy->toppings)[0]->type;

Large JSON Files
Handle large JSON files using:

• Processing large JSON files in PHP
• How to properly iterate through a big json file

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