php面试题汇集2

1、实现中文字符串截取无乱码方法

开启mbstring扩展，然后自定义函数：

<?phpheader(‘content-Type:text/html:charset=utf-8‘);function substr_utf8($str, $start, $length = null) {return join("",array_slice(preg_split("//u", $str, -1, PREG_SPLIT_NO_EMPTY), $start, $length));}//实例$str = "我是一个good男孩!";echo substr_utf8($str, 2, 4);

2、用PHP打印前一天的时间

<?phpheader(‘content-Type:text/html:charset=utf-8‘);echo date(‘Y-m-d H:i:s‘,strtotime(‘-1 day‘));

3、不适用第三个变量交换2个变量的值

<?phpheader(‘content-Type:text/html:charset=utf-8‘);$a = ‘a‘;$b = ‘b‘;list($a,$b) = array($b,$a);echo $a,$b;

4、将1234567890，转换成1,234,567,890

header(‘content-Type:text/html:charset=utf-8‘);$str = ‘1234567890‘;//反转字符串$str = strrev($str);//使用逗号分隔得到098,765,432,1,$str = chunk_split($str,3,‘,‘);//再次反转$str = strrev($str);//去掉左边的,$str = ltrim($str,‘,‘);echo $str;

5、实现utf8字符串反转

不能使用strrev，中文会出错

function strrev_utf8($str){return join("",array_reverse(preg_split("//u",$str)));}$str = "我是一个good男孩";echo strrev_utf8($str);

6、取url的文件扩展名，尽量多的去实现方法

$str = "www.baidu.com/index.php";function get_ext1($str){return strrchr($str,‘.‘);}function get_ext2($str){return substr($str,strrpos($str,‘.‘));}function get_ext3($str){$str = pathinfo($str);return $str[‘extension‘];}function get_ext4($str){$arr = explode(‘.‘,$str);return $arr[count($arr)-1];}function get_ext5($str){$pattern = ‘/^[^\.]+\.([\w]+)$/‘;return preg_replace($pattern,‘${1}‘,basename($str));}

7、写一个函数，将字符串open_door转换为OpenDoor

$str = "open_door";function change_str($str){$arr = explode(‘_‘,$str);$arr = array_map(‘ucfirst‘,$arr);return implode(‘‘,$arr);}echo change_str($str);

8、单例模式

<?phpclass Mysql{private static $instance = null;private $conn;//设置为私有，不允许通过new获得对象private function __construct(){$conn = mysql_connect(‘localhost‘,‘root‘,‘123456‘);}//获取实例方法public static function getInstance(){if(! self::$instance instanceof self){self::$instance = new self;}return self::$instance;}//禁止克隆private function __clone(){}}$db = Mysql::getInstance();

9、写一段PHP代码，确保多个进程同时写入同一个文件成功

<?php$fp = fopen("lock.txt","w+");if(flock($fp,LOCK_EX)){//获得写锁fwrite($fp,‘write something‘);flock($fp,LOCK_UN);}else{echo "file is locking...";}fclose($fp);

10、从一个完成的url获取文件扩展名

<?php$url = ‘http://www.baidu.com/a/b/index.php?id=1‘;$arr = parse_url($url);$fname = basename($arr[‘path‘]);$arr = explode(‘.‘,$fname);echo $arr[count($arr)-1];

11、写一个函数可以便利一个文件夹下的所有文件和子文件夹

<?phpfunction my_scandir($dir){$files = array();if(is_dir($dir)){if($handle = opendir($dir)){while(($file = readdir($handle)) !== false){if($file != "." && $file != ".."){if(is_dir($dir.‘/‘.$file)){$files[$file] = my_scandir($dir.‘/‘.$file);}else{$files[] = $dir.‘/‘.$file;}}}closedir($handle);return $files;}}}var_dump(my_scandir(‘D:\wamp\www\study‘));

12、论坛中无限分类实现原理

首先设计数据库表

create table category(cate_id int unsigned not null auto_increment primary key,cat_name varchar(30) not null default ‘‘,parent_id int unsigned not null default 0) engine=innodb charset=utf8;

然后用函数去递归实现，无限分类

function tree($arr,$pid=0,$level=0){static $list = array();foreach($arr as $v){//如果是顶级分类，则存入$list//然后以此节点为根几点，遍历其子节点if($v[‘parent_id‘] == $pid){$v[‘level‘] = $level;$list[] = $v;tree($arr,$v[‘cat_id‘],$level+1);}}return $list;}

13、计算2个文件的相对路径

<?php$a = ‘/a/b/c/d/a.php‘;$b = ‘/a/b/e/f/b.php‘;$arr1 = explode(‘/‘,dirname($a));$arr2 = explode(‘/‘,dirname($b));for($i=0,$len=count($arr2);$i<$len;$i++){if($arr1[$i] != $arr2[$i]){break;}}//不在用一个根目录if($i == 1){$ret = array();}//在同一个根目录下if($i != 1 && $i < $len){$ret = array_fill(0,$len-$i,"..");}//在同一个目录下if($i == $len){$ret = array(‘./‘);}$ret = array_merge($ret,array_slice($arr1,$i));echo implode(‘/‘,$ret);

14、约瑟夫环问题

<?phpfunction king($n,$m){$monkey = range(1,$n);$i = 0;while(count($monkey) > 1){$i += 1;$head = array_shift($monkey);//一个个出列最前面的if( $i % $m != 0){//如果不是m的倍数，则返回尾部，否则就出列了array_push($monkey,$head);}}return $monkey[0];}echo king(10,7);

15、PHP实现双向队列

<?phpclass Dqueue{private $queue = array();public function addFirst($item){return array_unshift($this->queue,$item);}public function addLast($item){return array_push($this->queue,$item);}public function getFirst(){return array_shift($this->queue);}public function getLast(){return array_pop($this->queue);}}