Linq in PHP

This is PHP library, that allows to query collections following C# LINQ patterns. The standard LINQ methods are implemented with interfaces adopted to the PHP language. The full list of these methods can be taken from MSDN, .NET 4.5. The modified interfaces of these methods are located in the Qmaker\Linq\Operation namespace. At the present time the library requires PHP of the version 5.4.

Lambda expression

The class Lambda allows to build lambda expressions, anonymous functions with stored structure. The class creates a callable object, which can be used in LINQ methods as callable criteria, predicate or expression. Thus,

$f = Lambda::define()->x()->add()->v()->mult(12)->gt(36);

or

$f = Lambda::define('x+x*12>36');

are equivalent to

$f = function ($x) { return $x + $x*12 > 36; };

but include also information about the expression structure.

More information and examples will be added later. See unit tests.

Linq

The following methods are implemented

• Aggregation — aggregate, average, min, max, sum, count
• Concatenation — concat, zip
• Element — elementAt, elementAtOrDefault, first, firstOrDefault, last, lastOrDefault, single, singleOrDefault
• Equality — isEqual
• Filtering — ofType, where
• Generation — from, range, repeat, empty_, defaultIfEmpty
• Grouping — groupBy
• Joining — product, join, joinOuter, groupJoin
• Partitioning — skip, skipWhile, take, takeWhile
• Projection — select, selectMany, cast
• Quantifier — all, any, contains
• Set — distinct, intersect, except, union
• Sorting — orderBy, orderByDescending, thenBy, thenByDescending, reverse, order
• Others — toArray, toList, asEnumerable, toLookup, toDictionary, each

The suited types for the source in the corresponding methods (like from or join) are array, \Iterator, \IteratorAggregate or callable variable. As an expression parameter one can also specify string, callable variable, array or lambda expression. The following example

$f = Linq::from([1, 2, 3, 4])->where((new Lambda())->x()->gt(2))->sum((new Lambda())->x()->mult(2));

will return 14. More information and examples will be added later. See unit tests.

Iterators

The iterators are the keystone of this library. Within the project multiple iterators were additionally implemented

• CallbackFilterIterator Filtering items using multiple callbacks

• CallbackIterator Generate the sequence of the elements using a callback

• GroupingIterator Group elements by key

• IndexIterator Sort elements by key

• JoinIterator, OuterJoinIterator Inner/outer join of two iterators

• LimitIterator Iterator over the given range

• ProductIterator Cross-product of multiple iterators

• SkipIterator Skip items while some criteria is true

• TakeIterator Take items while some criteria is true

• ProjectionIterator Convert current values or keys

• ReverseIterator Reverse order

• DistinctIterator, ExceptIterator, IntersectIterator Sets operations

• LazyIterator Build inner iterator when the first item will be requested

• VariableIterator Re-assign the inner iterator