PHP 7.3 – JSON_THROW_ON_ERROR, flexible Heredoc, array_key_first/last

PHP 7.3 was officially released in December 2018. Not a revolution, but a few changes have a real impact on everyday code – especially working with JSON, more flexible Heredoc syntax, and a handful of new array functions.

json_decode() with exceptions instead of silent failures

Before PHP 7.3, malformed JSON simply returned null – no exception, no error. You always had to check json_last_error(). PHP 7.3 adds JSON_THROW_ON_ERROR:

// PHP 7.3 - exception on parse error
try {
    $data = json_decode('{"broken: json}', true, 512, JSON_THROW_ON_ERROR);
} catch (\JsonException $e) {
    echo $e->getMessage(); // Syntax error
}

// Works with json_encode() too
try {
    $encoded = json_encode(['key' => "±1"], JSON_THROW_ON_ERROR);
} catch (\JsonException $e) {
    echo $e->getMessage(); // Malformed UTF-8 characters
}

Flexible Heredoc and Nowdoc

Before PHP 7.3 the closing marker had to be at column zero. PHP 7.3 allows indentation:

// PHP 7.3 - closing marker can be indented
function buildQuery(): string
{
    return <<<SQL
        SELECT *
        FROM orders
        WHERE status = 'pending'
        SQL;
}

array_key_first() and array_key_last()

$data = ['apple' => 1, 'banana' => 2, 'cherry' => 3];

// PHP 7.3 - direct
$firstKey = array_key_first($data); // 'apple'
$lastKey  = array_key_last($data);  // 'cherry'

is_countable() – end of warnings on PHP 7.2

function countItems($items): int
{
    if (!is_countable($items)) {
        return 0;
    }
    return count($items);
}

Summary

JSON_THROW_ON_ERROR is a change worth adopting immediately – it eliminates an entire class of silent failures when working with APIs. Flexible Heredoc is useful for long SQL queries or XML templates in Magento modules.