PHP中的Linq-用SQL语法操作PHP数组

由于很多时候需要涉及到数据库方面的例子,建个数据库对新手来说或许又要学多一样东西.
以后本站的例子,都会基于php及PHPLing库来开发.(本来打算用asp.net的,看了一下空间费用都比较贵.)

最近在看.net的新功能Linq,第一感觉,功能非常实用.
数组,字符串都可以用我们熟悉的 SQL 方式来查询,太方便啦!
就想看看PHP在这方面有没有这样的类库.

不查不知道,一查吓一跳,还真的有类似的类库,命名为PHPLinq.
PHPLinq的首页:
http://www.codeplex.com/PHPLinq
Examples

Examples can be found in the test package in the latest release.

A basic example

Let's say we have an array of strings and want to select only the strings whose length is < 5. The PHPLinq way of achieving this would be the following:

// Create data source$names = array("John", "Peter", "Joe", "Patrick", "Donald", "Eric"); $result = from('$name')->in($names) ->where('$name => strlen($name) < 5') ->select('$name');
Feels familiar to SQL? Yes indeed! No more writing a loop over this array, checking the string's length, and adding it to a temporary variable.

You may have noticed something strange... What's that $name => strlen($name) < 5 doing? This piece of code is compiled to an anonymous function or Lambda expression under the covers. This function accepts a parameter $name, and returns a boolean value based on the expression strlen($name) < 5.

An advanced example

There are lots of other examples available in the PHPLinq download, but here's an advanced one... Let's say we have an array of Employee objects. This array should be sorted by Employee name, then Employee age. We want only Employees whose name has a length of 4 characters. Next thing: we do not want an Employee instance in our result. Instead, the returning array should contain objects containing an e-mail address and a domain name.

First of all, let's define our data source:

class Employee { public $Name; public $Email; public $Age; public function __construct($name, $email, $age) { $this->Name = $name; $this->Email = $email; $this->Age = $age; }} $employees = array( new Employee('Maarten', 'maarten@example.com', 24), new Employee('Paul', 'paul@example.com', 30), new Employee('Bill', 'bill.a@example.com', 29), new Employee('Bill', 'bill.g@example.com', 28), new Employee('Xavier', 'xavier@example.com', 40));
Now for the PHPLinq query:

$result = from('$employee')->in($employees) ->where('$employee => strlen($employee->Name) == 4') ->orderBy('$employee => $employee->Name') ->thenByDescending('$employee => $employee->Age') ->select('new { "EmailAddress" => $employee->Email, "Domain" => substr($employee->Email, strpos($employee->Email, "@") + 1) }');
Again, you may have noticed something strange... What's this new { } thing doing? Actually, this is converted to an anonymous type under the covers. new { "name" => "test" } is evaluated to an object containing the property "name" with a value of "test".