atk4\data\Field::normalize PHP Method

    public function normalize($value)
    {
        if (!$this->owner->strict_types) {
            return $value;
        }
        if ($value === null) {
            return;
        }
        $f = $this;
        // only string type fields can use empty string as legit value, for all
        // other field types empty value is the same as no-value, nothing or null
        if ($f->type && $f->type != 'string' && $value === '') {
            return;
        }
        switch ($f->type) {
            case 'string':
                if (!is_scalar($value)) {
                    throw new Exception('Field value must be a string');
                }
                $value = trim($value);
                break;
            case 'integer':
                if (!is_numeric($value)) {
                    throw new Exception('Field value must be an integer');
                }
                $value = (int) $value;
                break;
            case 'float':
                if (!is_numeric($value)) {
                    throw new Exception('Field value must be a float');
                }
                $value = (double) $value;
                break;
            case 'money':
                if (!is_numeric($value)) {
                    throw new Exception('Field value must be numeric');
                }
                $value = round($value, 4);
                break;
            case 'boolean':
                if (is_bool($value)) {
                    break;
                }
                if (isset($f->enum) && is_array($f->enum)) {
                    if (isset($f->enum[0]) && $value === $f->enum[0]) {
                        $value = false;
                    } elseif (isset($f->enum[1]) && $value === $f->enum[1]) {
                        $value = true;
                    }
                } elseif (is_numeric($value)) {
                    $value = (bool) $value;
                }
                if (!is_bool($value)) {
                    throw new Exception('Field value must be a boolean');
                }
                break;
            case 'date':
            case 'datetime':
            case 'time':
                $class = isset($f->dateTimeClass) ? $f->dateTimeClass : 'DateTime';
                if (is_numeric($value)) {
                    $value = new $class('@' . $value);
                } elseif (is_string($value)) {
                    $value = new $class($value);
                } elseif (!$value instanceof $class) {
                    throw new Exception(['Field value must be a ' . $f->type, 'class' => $class, 'value class' => get_class($value)]);
                }
                break;
            case 'array':
                if (!is_array($value)) {
                    throw new Exception('Field value must be a array');
                }
                break;
            case 'object':
                if (!is_object($value)) {
                    throw new Exception('Field value must be a object');
                }
                break;
            case 'int':
            case 'str':
            case 'bool':
                throw new Exception(['Use of obsolete field type abbreviation. Use "integer", "string", "boolean" etc.', 'type' => $f->type]);
                break;
        }
        return $value;
    }