Check if a value can be json_decoded

can_json_decode.php

<?php

function try_json_encode($data)
{
    json_encode($data);
    return (json_last_error() == JSON_ERROR_NONE);
}

function json_encode_type_check($data)
{
    static $validTypes = [
        'string' => true,
        'integer' => true,
        'double' => true,
        'boolean' => true,
        'array' => true,
        'null' => true,
    ];

    $type = gettype($data);

    return isset($validTypes[$type])
        || $type == 'object' and $data instanceof JsonSerializable;
}

function benchmark($f, $iterations, ...$args)
{
    $startTime = microtime(true);
    for ($i = 0; $i < $iterations; $i++) {
        $f(...$args);
    }
    return ((microtime(true) - $startTime) / $iterations) * 1e9;
}

$iterations = 10000;

$cases = [
    'associative' => ['foo' => ['bar', 'baz', ['bam' => false]]],
    'boolean' => true,
    'string' => 'foobaz',
    'number' => -1,
    'deep assoc' => ['foo' => ['bar', 'baz', ['bam' => false]], ['foo' => ['bar', 'baz', ['bam' => false]]]],
];

$benches = ['try_json_encode', 'json_encode_type_check'];
foreach ($cases as $caseName => $case) {
    foreach ($benches as $bench) {
        $result = benchmark($bench, $iterations, $case);
        printf("%-20s %-30s: %-20f ns/iter\n", $caseName, $bench, $result);
    }
    echo "----\n";
}

Example output:

associative          try_json_encode               : 630.497932           ns/iter
associative          json_encode_type_check        : 306.200981           ns/iter
----
boolean              try_json_encode               : 198.483467           ns/iter
boolean              json_encode_type_check        : 634.384155           ns/iter
----
string               try_json_encode               : 243.020058           ns/iter
string               json_encode_type_check        : 376.105309           ns/iter
----
number               try_json_encode               : 348.401070           ns/iter
number               json_encode_type_check        : 248.122215           ns/iter
----
deep assoc           try_json_encode               : 813.007355           ns/iter
deep assoc           json_encode_type_check        : 308.108330           ns/iter
----

There can be objects wich are not instances of JsonSerializable which can be json_encoded.

<?php

$obj = new StdClass();

$obj->a = "b";

var_dump($obj instanceof JsonSerializable);
var_dump(json_encode($obj));