Belt 是 PHP 便捷开发工具。
Belt 主要特性：
60+ 的有用函数
经过完整的测试
代码清晰明了，文档齐全
Belt 包括：
boolean isDate(mixed $value)
boolean isNumber(mixed $value)
boolean isString(mixed $value)
boolean isFunction(mixed $value)
boolean isEmpty(mixed $value)
boolean isEqual(mixed $left, mixed $right)
boolean isBoolean(mixed $value)
boolean isObject(mixed $value)
boolean isArray(mixed $value)
boolean isTraversable(mixed $value)
boolean isNull(mixed $value)
boolean has(mixed $object, string $key)
array keys(mixed $object)
array values(mixed $object)
array methods(mixed $object)
mixed copy(mixed $value)
mixed extend(mixed $source, mixed $destination)
mixed apply(mixed $object, Closure $closure)
mixed defaults(mixed $object, array|mixed $defaults)
string escape(string $string)
string id(string $prefix = '')
mixed with(mixed $value)
void times(integer $number, Closure $closure)
mixed cache(Closure $closure)
mixed wrap(Closure $closure, Closure $wrapper)
mixed compose(array $closures, array $arguments = array())
void once(Closure $closure)
mixed after(integer $number, Closure $closure)
mixed|array first(array $elements, integer $amount = 1)
array initial(array $elements, integer $amount = 1)
array rest(array $elements, integer $index = 1)
mixed|array last(array $elements, integer $amount = 1)
array pack(array $elements)
array flatten(array $elements)
array range(integer $to, integer $from = 0, integer $step = 1)
array difference(array $one, array $another)
array unique(array $elements, Closure $iterator = null)
array without(array $elements, array $ignore)
array zip(array $one, array $another)
integer indexOf(array $elements, mixed $element)
array intersection(array $one, array $another)
array union(array $one, array $another)
void each(array $collection, Closure $iterator)
array map(array $collection, Closure $iterator)
array toArray(mixed $value)
integer|null size(array|Countable $value)
array shuffle(array $collection)
boolean any(array $collection, Closure $iterator)
boolean all(array $collection, Closure $iterator)
array reject(array $collection, Closure $iterator)
array pluck(array $collection, string $key)
boolean contains(array $collection, mixed $value)
array invoke(array $collection, string $function)
mixed reduce(array $collection, Closure $iterator, mixed $initial = 0)
array sortBy(array $collection, Closure $iterator)
array groupBy(array $collection, Closure $iterator)
mixed max(array $collection)
mixed min(array $collection)
简单示例：
use Belt\Belt;Belt::max([1, 2, 3]) // => 3Belt::flatten([1, [2, [3]]]) // => [1, 2, 3]Belt::last([1, 2, 3], 2) // => [2, 3]
项目主页：http://www.open-open.com/lib/view/home/1430832041179
