simdjson_php

simdjson_php bindings for the simdjson project.

Requirement

• PHP 7.0+ (The latest php version was 8.2 at the time of writing)
• Prerequisites: g++ (version 7 or better) or clang++ (version 6 or better), and a 64-bit system with a command-line shell (e.g., Linux, macOS, freeBSD). We also support programming environments like Visual Studio and Xcode, but different steps are needed

Installing

Linux

simdjson may also be installed with the command pecl install simdjson (You will need to enable simdjson in php.ini)

Alternately, you may wish to build from source.

MacOS

pecl install simdjson is the recommended installation method (You will need to enable simdjson in php.ini)

Alternately, you may wish to build from source.

Installing on Windows

Prebuilt DLLs can be downloaded from PECL once the PHP for Windows team fixes hardware issues.

See https://wiki.php.net/internals/windows/stepbystepbuild_sdk_2#building_pecl_extensions and .appveyor.yml for how to build this, in the meantime.

Compile simdjson_php in Linux

$ phpize
$ ./configure
$ make
$ make test
$ make install

Add the following line to your php.ini

extension=simdjson.so

simdjson_php Usage

$jsonString = <<<'JSON'
{
  "Image": {
    "Width":  800,
    "Height": 600,
    "Title":  "View from 15th Floor",
    "Thumbnail": {
      "Url":    "http://www.example.com/image/481989943",
      "Height": 125,
      "Width":  100
    },
    "Animated" : false,
    "IDs": [116, 943, 234, 38793, {"p": "30"}]
  }
}
JSON;

// Check if a JSON string is valid:
$isValid = simdjson_is_valid($jsonString); //return bool
var_dump($isValid);  // true

// Parsing a JSON string. similar to the json_decode() function but without the fourth argument
try {
    // returns array|stdClass|string|float|int|bool|null.
    $parsedJSON = simdjson_decode($jsonString, true, 512);
    var_dump($parsedJSON); // PHP array
} catch (RuntimeException $e) {
    echo "Failed to parse $jsonString: {$e->getMessage()}\n";
}

// note. "/" is a separator. Can be used as the "key" of the object and the "index" of the array
// E.g. "/Image/Thumbnail/Url" is recommended starting in simdjson 4.0.0,
// but "Image/Thumbnail/Url" is accepted for now.

// get the value of a "key" in a json string
// (before simdjson 4.0.0, the recommended leading "/" had to be omitted)
$value = simdjson_key_value($jsonString, "/Image/Thumbnail/Url");
var_dump($value); // string(38) "http://www.example.com/image/481989943"

$value = simdjson_key_value($jsonString, "/Image/IDs/4", true);
var_dump($value);
/*
array(1) {
  ["p"]=>
  string(2) "30"
}
*/

// check if the key exists. return true|false|null. "true" exists, "false" does not exist,
// throws for invalid JSON.
$res = simdjson_key_exists($jsonString, "/Image/IDs/1");
var_dump($res) //bool(true)

// count the values
$res = simdjson_key_count($jsonString, "/Image/IDs");
var_dump($res) //int(5)

simdjson_php API

<?php

/**
 * Takes a JSON encoded string and converts it into a PHP variable.
 * Similar to json_decode()
 *
 * @param string $json The JSON string being decoded
 * @param bool $associative When true, JSON objects will be returned as associative arrays.
 *                          When false, JSON objects will be returned as objects.
 * @param int $depth the maximum nesting depth of the structure being decoded.
 * @return array|stdClass|string|float|int|bool|null
 * @throws SimdJsonException for invalid JSON
 *                           (or $json over 4GB long, or out of range integer/float)
 * @throws SimdJsonValueError for invalid $depth
 */
function simdjson_decode(string $json, bool $associative = false, int $depth = 512) {}

/**
 * Returns true if json is valid.
 *
 * @param string $json The JSON string being decoded
 * @param int $depth the maximum nesting depth of the structure being decoded.
 * @return bool
 * @throws SimdJsonValueError for invalid $depth
 */
function simdjson_is_valid(string $json, int $depth = 512) : bool {}

/**
 * Parses $json and returns the number of keys in $json matching the JSON pointer $key
 *
 * @param string $json The JSON string being decoded
 * @param string $key The JSON pointer being requested
 * @param int $depth The maximum nesting depth of the structure being decoded.
 * @param bool $throw_if_uncountable If true, then throw SimdJsonException instead of
                                     returning 0 for JSON pointers
                                     to values that are neither objects nor arrays.
 * @return int
 * @throws SimdJsonException for invalid JSON or invalid JSON pointer
 *                           (or document over 4GB, or out of range integer/float)
 * @throws SimdJsonValueError for invalid $depth
 * @see https://www.rfc-editor.org/rfc/rfc6901.html
 */
function simdjson_key_count(string $json, string $key, int $depth = 512, bool $throw_if_uncountable = false) : int {}

/**
 * Returns true if the JSON pointer $key could be found.
 *
 * @param string $json The JSON string being decoded
 * @param string $key The JSON pointer being requested
 * @param int $depth the maximum nesting depth of the structure being decoded.
 * @return bool (false if key is not found)
 * @throws SimdJsonException for invalid JSON or invalid JSON pointer
 *                           (or document over 4GB, or out of range integer/float)
 * @throws SimdJsonValueError for invalid $depth
 * @see https://www.rfc-editor.org/rfc/rfc6901.html
 */
function simdjson_key_exists(string $json, string $key, int $depth = 512) : bool {}

/**
 * Returns the value at the json pointer $key
 *
 * @param string $json The JSON string being decoded
 * @param string $key The JSON pointer being requested
 * @param int $depth the maximum nesting depth of the structure being decoded.
 * @param bool $associative When true, JSON objects will be returned as associative arrays.
 *                          When false, JSON objects will be returned as objects.
 * @return array|stdClass|string|float|int|bool|null the value at $key
 * @throws SimdJsonException for invalid JSON or invalid JSON pointer
 *                           (or document over 4GB, or out of range integer/float)
 * @throws SimdJsonValueError for invalid $depth
 * @see https://www.rfc-editor.org/rfc/rfc6901.html
 */
function simdjson_key_value(string $json, string $key, bool $associative = false, int $depth = 512) {}

/**
 * An error thrown by simdjson when processing json.
 *
 * The error code is available as $e->getCode().
 * This can be compared against the `SIMDJSON_ERR_*` constants.
 *
 * Before simdjson 2.1.0, a regular RuntimeException with an error code of 0 was thrown.
 */
class SimdJsonException extends RuntimeException {
}

/**
 * Thrown for error conditions on fields such as $depth that are not expected to be
 * from user-provided JSON, with similar behavior to php 8.0.
 *
 * NOTE: https://www.php.net/valueerror was added in php 8.0.
 * In older php versions, this extends Error instead.
 *
 * When support for php 8.0 is dropped completely,
 * a major release of simdjson will likely switch to a standard ValueError.
 */
class SimdJsonValueError extends ValueError {
}

Edge cases

There are some differences from json_decode() due to the implementation of the underlying simdjson library. This will throw a RuntimeException if simdjson rejects the JSON.

Note that the simdjson PECL is using a fork of the simdjson C library to imitate php's handling of integers and floats in JSON.

1. Until simdjson 2.1.0, simdjson_decode() differed in how out of range 64-bit integers and floats are handled.

See https://github.com/simdjson/simdjson/blob/master/doc/basics.md#standard-compliance

• The specification allows implementations to set limits on the range and precision of numbers accepted. We support 64-bit floating-point numbers as well as integer values.
  • We parse integers and floating-point numbers as separate types which allows us to support all signed (two's complement) 64-bit integers, like a Java long or a C/C++ long long and all 64-bit unsigned integers. When we cannot represent exactly an integer as a signed or unsigned 64-bit value, we reject the JSON document.
  • We support the full range of 64-bit floating-point numbers (binary64). The values range from std::numeric_limits<double>::lowest() to std::numeric_limits<double>::max(), so from -1.7976e308 all the way to 1.7975e308. Extreme values (less or equal to -1e308, greater or equal to 1e308) are rejected: we refuse to parse the input document. Numbers are parsed with a perfect accuracy (ULP 0): the nearest floating-point value is chosen, rounding to even when needed. If you serialized your floating-point numbers with 17 significant digits in a standard compliant manner, the simdjson library is guaranteed to recover the same numbers, exactly.

2. The maximum string length that can be passed to simdjson_decode() is 4GiB (4294967295 bytes). json_decode() can decode longer strings.

3. The handling of max depth is counted slightly differently for empty vs non-empty objects/arrays. In json_decode, an array with a scalar has the same depth as an array with no elements. In simdjson_decode, an array with a scalar is one level deeper than an array with no elements. For typical use cases, this shouldn't matter. (e.g. simdjson_decode('[[]]', true, 2) will succeed but json_decode('[[]]', true, 2) and simdjson_decode('[[1]]', true, 2) will fail.)

Benchmarks

See the benchmark folder for more benchmarks.