[BUG][PHP] Fix declaration parsing <array(type, type)> in description

Wrong substr number in case of array<....>. There could be or 4 (map[) or 6 (array<) depending which keyword is used in $class.

https://github.com/OpenAPITools/openapi-generator/blob/1d648223e6fdc1adad8967db05d86db9fc49a581/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache#L281

Additionally, if space is used between key and type (e.g. <array(string, int)>), the $subClass should be trimmed.

Here is how to do it without calling substr:

if (preg_match('/^(?:array|map)[<\[](.*)[>\]]$/', $class, $matchedValues)) { // for associative array e.g. array<string,int>
    $data = is_string($data) ? json_decode($data) : $data;
    settype($data, 'array');
    $inner = $matchedValues[1];
    $deserialized = [];
    if (false !== strpos($inner, ',')) {
        $subClass_array = explode(',', $inner, 2);
        $subClass = trim($subClass_array[1]);
        foreach ($data as $key => $value) {
            $deserialized[$key] = self::deserialize($value, $subClass, null);
        }
    }
    return $deserialized;
}

Start at modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache#L281 and inspect how declaration strings are parsed for map[...] and array<...>. Check the existing deserialization flow against array(string, int) and spacing around the inner type. Done means both declaration forms parse the intended subtype without leaving surrounding whitespace.