1 simhash的原理，比较详细的参考链接： 2 simhash的php实现（如下）。主要用到了php的类库gmp 3 ps：oshchina代码编辑器真心难用，大家将就一下。。以后改好哈。希望能改进！！ 4 因为工作原因用php重写了simhash算法

        
    m_hashbits = $hashbits;        $this->m_hash = $this->simhash($tokens);    }    //to string    public function __toString()    {        return strval($this->m_hash);    }    //返回hash值    public function simhash($tokens)    {        if(!is_array($tokens))        {                     throw new Exception("tokens should be array");        }        $v = array_fill(0,$this->m_hashbits,0);        foreach($tokens as $x)        {            $x = $this->stringHash($x);            for($i=0;$i<$this->m_hashbits;$i++)            {                $bitmask = gmp_init(1);                gmp_setbit($bitmask, $i);                $bitmask = gmp_sub($bitmask,1);                if (gmp_strval(gmp_and($x,$bitmask)) != "0")                {                    $v[$i] += 1;                }                else                {                    $v[$i] -= 1;                }            }        }        $sum = 0;        for($i=0;$i<$this->m_hashbits;$i++)        {            if ($v[$i] >= 0)            {                $num = gmp_init(1);                gmp_setbit($num, $i);                $num = gmp_sub($num,1);                $sum = gmp_add($sum,$num);            }        }        return gmp_strval($sum);    }    //求海明距离    public function hammingDistance($other)    {        $a = gmp_init($this->m_hash);        $b = gmp_init($other->m_hash);        $c = gmp_init(1);        gmp_setbit($c, $this->m_hashbits);        $c = gmp_sub($c,2);        $x = gmp_and(gmp_xor($a,$b),$c);        $tot = 0;        while(gmp_strval($x))        {            $tot += 1;            $x = gmp_and($x,gmp_sub($x,1));        }        return $tot;    }    //求相似度    public function similarity ($other)    {        $a = floatval($this->m_hash);        $b = floatval($other->m_hash);        if($a > $b)        {            return $b/$a;        }        else        {            return $a/$b;        }    }        public function stringHash($source)    {        if(empty($source))        {            return 0;        }        else        {            $x = ord($source[0]) << 7;                        $m = 1000003;                        $mask = gmp_sub(gmp_pow("2", $this->m_hashbits),1);            $len = strlen($source);                        for($i=0;$i<$len;$i++)            {                $x = gmp_and(gmp_xor(gmp_mul($x,$m),ord($source[$i])),$mask);            }            $x = gmp_xor($x,$len);            if(intval(gmp_strval($x)) == -1)            {                $x = -2;            }            return $x;        }    }}$s = 'This is a test string for testing';$hash1 = new Simhash(explode(" ",$s));$s = 'This is a test string for testing also';$hash2 = new Simhash(explode(" ",$s));$s = 'nai nai ge xiong cao';$hash3 = new Simhash(explode(" ",$s));var_dump($hash1->hammingDistance($hash2) , "   " , $hash1->similarity($hash2));var_dump($hash1->hammingDistance($hash3) , "   " , $hash1->similarity($hash3));