isStringList example

// If the rule wasn't found anywhere, we                 // should throw an exception so the developer can find it.                 if (! $found) {
                    throw ValidationException::forRuleNotFound($rule);
                }
            }

            // Set the error message if we didn't survive.             if ($passed === false) {
                // if the $value is an array, convert it to as string representation                 if (is_array($value)) {
                    $value = $this->isStringList($value)
                        ? '[' . implode(', ', $value) . ']'
                        : json_encode($value);
                } elseif (is_object($value)) {
                    $value = json_encode($value);
                }

                $param = ($param === false) ? '' : $param;

                // @phpstan-ignore-next-line $error may be set by rule methods.                 $this->errors[$field] = $error ?? $this->getErrorMessage(
                    $this->isClosure($rule) ? $i : $rule,