# How to Work with Currencies

To use `Zend_Currency` within your application, create an instance of it without any parameters. This will create an instance of `Zend_Currency` with your locale set and defines the currency which should be used for this locale.

## Creating an Instance of Zend_Currency from the Locale

Assume you have 'en_US' set as the set locale by the user or your environment. By passing no parameters while creating the instance you tell `Zend_Currency` to use the currency from the locale 'en_US'. This leads to an instance with US Dollar set as the currency with formatting rules from 'en_US'.

    $currency = new Zend_Currency();

`Zend_Currency` also supports the usage of an application-wide locale. You can set a `Zend_Locale` instance in the registry as shown below. With this notation you can avoid setting the locale manually for each instance when you want to use the same locale throughout the application.

    // in your bootstrap file
    $locale = new Zend_Locale('de_AT');
    Zend_Registry::set('Zend_Locale', $locale);

    // somewhere in your application
    $currency = new Zend_Currency();

If your system has no default locale, or if the locale of your system can not be detected automatically, `Zend_Currency` will throw an exception. If see this exception, you should consider setting the locale manually.

Depending on your needs, several parameters can be speicified at instantiation. Each of these parameters is optional and can be omitted. Even the order of the parameters can be switched. The meaning of each parameter is described in this list:

- currency:

  A locale can include several currencies. Therefore the first parameter 'currency' can define which currency should be used by giving the short name or full name of that currency. If that currency in not recognized in any locale an exception will be thrown. Currency short names are always made up of 3 letters, written in uppercase. Well known currency shortnames include USD or EUR.

- locale:

  The 'locale' parameter defines which locale should be used for formatting the currency. The specified locale will also be used to get the script and symbol for this currency if these parameters are not given.

  Note that `Zend_Currency` only accepts locales which include a region. This means that all locales that only include a language will result in an exception. For example the locale en will cause an exception to be thrown whereas the locale en_US will return USD as currency.

## Other Ways to Create Instances of Zend_Currency

    // expect standard locale 'de_AT'

    // creates an instance from 'en_US' using 'USD' which is default
    // currency for 'en_US'
    $currency = new Zend_Currency('en_US');

    // creates an instance from the set locale ('de_AT') using 'EUR' as
    // currency
    $currency = new Zend_Currency();

    // creates an instance using 'EUR' as currency, 'en_US' for number
    // formating
    $currency = new Zend_Currency('en_US', 'EUR');

You can omit any of the parameters to `Zend_Currency`'s constructor if you want to use the default values. This has no negative effect on handling the currencies. It can be useful if, for example, you don't know the default currency for a region.

For many countries there are several known currencies. Typically, one currency will currently be in use, with one or more ancient currencies. If the 'currency' parameter is suppressed the contemporary currency will be used. The region 'de' for example knows the currencies 'EUR' and 'DEM'... 'EUR' is the contemporary currency and will be used if the currency parameter is omitted.

## Creating and Output String from a Currency

To get a numeric value converted to an output string formatted for the currency at hand, use the method `toCurrency()`. It takes the value which should be converted. The value itself can be any normalized number.

If you have a localized number you will have to convert it first to an normalized number with Zend_Locale_Format::getNumber(). It may then be used with `toCurrency()` to create a currency output string.

`toCurrency(array $options)` accepts an array with options which can be used to temporarily set another format or currency representation. For details about which options can be used see Changing the Format of a Currency.

### Creating an Output String for a Currency

    // creates an instance with 'en_US' using 'USD', which is the default
    // values for 'en_US'
    $currency = new Zend_Currency('en_US');

    // prints '$ 1,000.00'
    echo $currency->toCurrency(1000);

    // prints '$ 1.000,00'
    echo $currency->toCurrency(1000, array('format' => 'de_AT'));

    // prints '$ ١٬٠٠٠٫٠٠'
    echo $currency->toCurrency(1000, array('script' => 'Arab'));

## Changing the Format of a Currency

The format which is used by creation of a `Zend_Currency` instance is, of course, the standard format. But occasionally it is necessary to change this format.

The format of an currency output includes the following parts:

- Currency symbol, shortname or name:

  The symbol of the currency is normally displayed within the currency output string. It can be suppressed when needed or even overwritten.

- Currency position:

  The position of the currency symbol is normally automatically defined by the locale. It can be changed if necessary.

- Script:

  The script which shall be used to display digits. Detailed information about scripts and their usage can be found in the documentation of `Zend_Locale` in the chapter Numeral System Conversion.

- Number formatting:

  The amount of currency (formally known as value of money) is formatted by the usage of formatting rules within the locale. For example is in English the ',' sign used as separator for thousands, and in German the '.' sign.

So if you need to change the format, you should the `setFormat()` method. It takes an array which should include every option you want to change. The `$options` array supports the following settings:

- position: Defines the position at which the currency description should be displayed. The supported positions can be found in this table.

- script: Defined which script should be used for displaying digits. The default script for most locales is 'Latn', which includes the digits 0 to 9. Other scripts such as 'Arab' (Arabian) can be used.

- format: Defines the format which should be used for displaying numbers. This number-format includes for example the thousand separator. You can eighter use a default format by giving a locale identifier, or define the number-format manually. If no format is set the locale from the `Zend_Currency` object will be used.

- display: Defines which part of the currency should be used for displaying the currency representation. There are 4 representations which can be used and which are all described in this table.

- precision: Defines the precision which should be used for the currency representation. The default value is 2.

- name: Defines the full currency name which should be displayed. This option overwrites any currency name which is set through the creation of `Zend_Currency`.

- currency: Defines the international abbreviation which should be displayed. This option overwrites any abbreviation which is set through the creation of `Zend_Currency`.

- symbol: Defines the currency symbol which should be displayed. This option overwrites any symbol which is set through the creation of `Zend_Currency`.

### Constants for the selecting the currency description

constant | description
--- | ---
`NO_SYMBOL` | Do not display any currency representation
`USE_SYMBOL` | Display the currency symbol
`USE_SHORTNAME` | Display the 3 lettered international currency abbreviation
`USE_NAME` | Display the full currency name

### Constants for the selecting the position of the currency description

constant | description
--- | ---
`STANDARD` | Set the standard position as defined within the locale
`RIGHT` | Display the currency representation at the right side of the value
`LEFT` | Display the currency representation at the left side of the value

### Changing the displayed format of a currency

    // creates an instance with 'en_US' using 'USD', 'Latin' and 'en_US' as
    // these are the default values from 'en_US'
    $currency = new Zend_Currency('en_US');

    // prints 'US$ 1,000.00'
    echo $currency->toCurrency(1000);

    $currency->setFormat(array('display' => Zend_Currency::USE_NAME,
                               'position' => Zend_Currency::RIGHT));

    // prints '1.000,00 US Dollar'
    echo $currency->toCurrency(1000);

    $currency->setFormat(array('name' => 'American Dollar'));
    // prints '1.000,00 American Dollar'
    echo $currency->toCurrency(1000);

    $currency->setFormat(array('format' => '##0.00'));
    // prints '1000,00 American Dollar'
    echo $currency->toCurrency(1000);

## Reference Methods for Zend_Currency

Of course, `Zend_Currency` supports also methods to get information about any existing and many ancient currencies from `Zend_Locale`. The supported methods are:

- `getSymbol()`:

  Returns the known symbol of the set currency or a given currency. For example $ for the US Dollar within the locale 'en_US.

- `getShortName()`:

  Returns the abbreviation of the set currency or a given currency. For example USD for the US Dollar within the locale 'en_US.

- `getName()`:

  Returns the full name of the set currency of a given currency. For example US Dollar for the US Dollar within the locale 'en_US.

- `getRegionList()`:

  Returns a list of regions where the set currency or a given one is known to be used. It is possible that a currency is used within several regions, so the return value is always an array.

- `getCurrencyList()`:

  Returns a list of currencies which are used in the given region.

The function `getSymbol()`, `getShortName()` and `getName()` accept two optional parameters. If no parameter is given the expected data will be returned from the set currency. The first parameter takes the shortname of a currency. Short names are always three lettered, for example EUR for euro or USD for US Dollar. The second parameter defines from which locale the data should be read. If no locale is given, the set locale is used.

### Getting Information about Currencies

    // creates an instance with 'en_US' using 'USD', 'Latin' and 'en_US'
    // as these are the default values from 'en_US'
    $currency = new Zend_Currency('en_US');

    // prints '$'
    echo $currency->getSymbol();

    // prints 'EUR'
    echo $currency->getShortName('EUR');

    // prints 'Österreichische Schilling'
    echo $currency->getName('ATS', 'de_AT');

    // returns an array with all regions where USD is used
    print_r($currency->getRegionList();

    // returns an array with all currencies which were ever used in this
    // region
    print_r($currency->getCurrencyList('de_AT');

## Settings new default values

The method `setLocale()` allows to set a new locale for `Zend_Currency`. All default values for the currency will be overwritten when this method is invoked. This includes currency name, abbreviation and symbol.

### Setting a New Locale

    // get the currency for US
    $currency = new Zend_Currency('en_US');
    print $currency->toCurrency(1000);

    // get the currency for AT
    $currency->setLocale('de_AT');
    print $currency->toCurrency(1000);

## Zend_Currency Performance Optimization

`Zend_Currency`'s performance can be optimized using `Zend_Cache`. The static method `Zend_Currency::setCache($cache)` accepts one option: a `Zend_Cache` adapter. If the cache adapter is set, the localization data that `Zend_Currency` uses are cached. There are some static methods for manipulating the cache: `getCache()`, `hasCache()`, `clearCache()` and `removeCache()`.

### Caching currencies

    // creating a cache object
    $cache = Zend_Cache::factory('Core',
                                 'File',
                                 array('lifetime' => 120,
                                       'automatic_serialization' => true),
                                 array('cache_dir'
                                           => dirname(__FILE__) . '/_files/'));
    Zend_Currency::setCache($cache);