How Can I Efficiently Process Large JSON Files in PHP Without Memory Issues?

Processing Large JSON Files in PHP

Handling voluminous JSON files can be a challenge, especially when dealing with potentially large files exceeding 200M in size. To address this issue, it is crucial to avoid loading the entire file into memory. Instead, a streaming approach is recommended to process objects individually without buffering the full content.

One effective solution is to utilize a streaming JSON pull parser like pcrov/JsonReader for PHP 7. This parser follows a different approach from event-based parsers by allowing you to explicitly request data by calling methods on the parser. This provides greater flexibility and control over the parsing process.

Example 1: Reading Objects as Whole Entities

This example demonstrates how to extract objects from the JSON file as complete arrays:

use pcrov\JsonReader\JsonReader;

$reader = new JsonReader();
$reader->open("data.json");

$reader->read(); // Outer array.
$depth = $reader->depth(); // Check in a moment to break when the array is done.
$reader->read(); // Step to the first object.
do {
    print_r($reader->value()); // Do your thing.
} while ($reader->next() && $reader->depth() > $depth); // Read each sibling.

$reader->close();

Example 2: Reading Individual Named Elements

To extract specific elements from each object, this example demonstrates:

$reader = new pcrov\JsonReader\JsonReader();
$reader->open("data.json");

while ($reader->read()) {
    $name = $reader->name();
    if ($name !== null) {
        echo "$name: {$reader->value()}\n";
    }
}

$reader->close();

Example 3: Filtering Properties by Name

This final example showcases how to filter properties by a specific name, even if duplicate names exist within the same object:

$json = <<<JSON
[
    {"property":"value", "property2":"value2"},
    {"foo":"foo", "foo":"bar"},
    {"prop":"val"},
    {"foo":"baz"},
    {"foo":"quux"}
]
JSON;

$reader = new pcrov\JsonReader\JsonReader();
$reader->json($json);

while ($reader->read("foo")) {
    echo "{$reader->name()}: {$reader->value()}\n";
}

$reader->close();

The optimal approach for processing large JSON files will vary depending on the structure of the data and the intended operations. However, by leveraging streaming JSON parsers, developers can efficiently handle voluminous JSON files without encountering memory issues.

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