四种比较常见的排序算法：插入，快速，选择，冒泡 以及测试程序

SortAlgorithm.php

<?php

/**
 * 排序算法
 * 插入排序、快速排序、选择排序、冒泡排序
 * 
 */
class SortAlgorithm{

	/**
	 * 插入排序
	 * 算法排序过程示例图: http://baike.baidu.com/picture/396887/396887/0/d57e99942da24e5dd21b7080?fr=lemma&ct=single#aid=0&pic=d57e99942da24e5dd21b7080 
	 * @param array $arr 待排序的数组
	 * @param string $mode 'asc' 'desc'
	 *
	 */
	public function insertSort(array $arr, $mode='asc'){
		$count = count($arr);
		for ($i=1; $i<$count; $i++){
			$j = $i-1;
			$insertEle = $arr[$i];

			while(array_key_exists($j, $arr) && self::getAgtBByMode($arr[$j], $insertEle, $mode)){
				$arr[$j+1] = $arr[$j];
				$arr[$j] = $insertEle;
				$j--;
			}
		}
		return $arr;
	}

	public function bubbleSort(array $arr, $mode='asc'){
		$count = count($arr);
		for($i=0; $i<$count; $i++){
			for($j=0;$j<$count-1-$i; $j++){
				if(self::getAgtBByMode($arr[$j], $arr[$j+1], $mode)){
					$tmp = $arr[$j+1];
					$arr[$j+1] = $arr[$j];
					$arr[$j] = $tmp;
				}
			}
		}
		return $arr;
	}

	/**
	 * 选择排序
	 * http://baike.baidu.com/view/547263.htm
	 */
	public function selectSort(array $arr, $mode='asc'){
		$count = count($arr);
		for ($i=0; $i<$count-1; $i++){
			$k = $i;
			for($j=$i+1; $j<$count; $j++){
				if(self::getAgtBByMode($arr[$k], $arr[$j], $mode)){
						$k=$j;
				}
			}
			if($k!=$i){
				$tmp = $arr[$k];
				$arr[$k] = $arr[$i];
				$arr[$i] = $tmp;
			}
		}
		return $arr;
	}

	/**
	 *
	 *
	 * http://baike.baidu.com/picture/19016/19016/0/574e9258d109b3dee4ddfa6acfbf6c81800a4c55?fr=lemma&ct=single#aid=0&pic=574e9258d109b3dee4ddfa6acfbf6c81800a4c55
	 *
	 */
	public function quickSort(array $arr, $mode='asc'){

		if(count($arr)>1){

			$key=$arr[0];
			$left=$right=array();
			$_size=count($arr);

			for($i=1;$i<$_size;$i++){

				if(self::getAgtBByMode($key, $arr[$i], $mode)){
					$left[] = $arr[$i];
				}else{
					$right[] = $arr[$i];
				}
			}

			$left=self::quickSort($left, $mode);
			$right=self::quickSort($right, $mode);

			return array_merge($left,array($key),$right);
		}else{
			return $arr;
		}
	}

	/**
	 * 比较两个数的大小，根据$mode的值来返回 true 或 false.
	 *
	 * 若传入的 $mode = asc 则 $a > $b 返回 true
	 * 若 $mode = desc 则 $a < $b 返回true
	 * 反之则返回  false 
	 *
	 * @param int $a
	 * @param int $b
	 * @param string $mode asc desc
	 * @return boolean
	 */
	protected static function getAgtBByMode($a, $b, $mode='asc'){
		$a = (int)$a;
		$b = (int)$b;
		return $mode == 'asc' ? $a > $b : $a < $b;
	}

}

SortAlgorithmTest.php

<?php

include __DIR__.'/../src/SortAlgorithm.php';

class SortAlgorithmTest extends PHPUnit_Framework_TestCase{
	protected $originalArr = array(77, 10, 77, 20, 30, 79, 22, 21,9, 100,50,43,21,89);
	protected $expectASCArr = array(9, 10, 20, 21, 21, 22, 30, 43, 50, 77, 77, 79, 89, 100);
	protected $expectDESCArr = array(100, 89, 79, 77, 77, 50,     43,30, 22, 21, 21, 20, 10, 9);

	protected $SortAlgorithm = null;

	public function setUp(){
		if($this->SortAlgorithm===null){
			$this->SortAlgorithm = new SortAlgorithm;
		}
	}

	public function tearDown(){
		$this->SortAlgorithm = null;
	}

	public function testBubbleSort(){
		
		$originalArr = $this->originalArr;
		shuffle($originalArr);

		$this->assertEquals($this->expectASCArr
			, $this->SortAlgorithm->bubbleSort($originalArr, 'asc'));

		$this->assertEquals($this->expectDESCArr
			, $this->SortAlgorithm->bubbleSort($originalArr, 'desc'));		
	}
	public function testInsertSort(){
		
		$originalArr = $this->originalArr;
		// 每次在进行排序之前，将原始数据打扰之后进行测试
		shuffle($originalArr);

		$this->assertEquals($this->expectASCArr
			, $this->SortAlgorithm->insertSort($originalArr, 'asc'));
		$this->assertEquals($this->expectDESCArr
			, $this->SortAlgorithm->insertSort($originalArr, 'desc'));
	}

	public function testSelectSort(){
		
		$originalArr = $this->originalArr;
		// 每次在进行排序之前，将原始数据打扰之后进行测试
		shuffle($originalArr);

		$this->assertEquals($this->expectASCArr
			, $this->SortAlgorithm->selectSort($originalArr, 'asc'));
		$this->assertEquals($this->expectDESCArr
			, $this->SortAlgorithm->selectSort($originalArr, 'desc'));
	}

	public function testQuickSort(){
		
		$originalArr = $this->originalArr;
		// 每次在进行排序之前，将原始数据打扰之后进行测试
		shuffle($originalArr);

		$this->assertEquals($this->expectASCArr
			, $this->SortAlgorithm->quickSort($originalArr, 'asc'));
		$this->assertEquals($this->expectDESCArr
			, $this->SortAlgorithm->quickSort($originalArr, 'desc'));
	}
}