Method getSha1

/**
 * Utility method to get the hash after removing selected values. This lets us detect changes other than
 * modified date (which will change on every save).
 *
 * @param   mixed        $jsonData   Either an object or a string with json-encoded data
 * @param   ContentType  $typeTable  Table object with data for this content type
 *
 * @return  string  SHA1 hash on success. Empty string on failure.
 *
 * @since   3.2
 */
public function getSha1($jsonData, ContentType $typeTable)
{
    $object = \is_object($jsonData) ? $jsonData : json_decode($jsonData);
    if (isset($typeTable->content_history_options) && \is_object(json_decode($typeTable->content_history_options))) {
        $options = json_decode($typeTable->content_history_options);
        $this->ignoreChanges = $options->ignoreChanges ?? $this->ignoreChanges;
        $this->convertToInt = $options->convertToInt ?? $this->convertToInt;
    }
    foreach ($this->ignoreChanges as $remove) {
        if (property_exists($object, $remove)) {
            unset($object->{$remove});
        }
    }
    // Convert integers, booleans, and nulls to strings to get a consistent hash value
    foreach ($object as $name => $value) {
        if (\is_object($value)) {
            // Go one level down for JSON column values
            foreach ($value as $subName => $subValue) {
                $object->{$subName} = \is_int($subValue) || \is_bool($subValue) || $subValue === null ? (string) $subValue : $subValue;
            }
        } else {
            $object->{$name} = \is_int($value) || \is_bool($value) || $value === null ? (string) $value : $value;
        }
    }
    // Work around empty values
    foreach ($this->convertToInt as $convert) {
        if (isset($object->{$convert})) {
            $object->{$convert} = (int) $object->{$convert};
        }
    }
    if (isset($object->review_time)) {
        $object->review_time = (int) $object->review_time;
    }
    return sha1(json_encode($object));
}