php中empty和isset用法区别详解

<?php

$a = array ('test' => 1, 'hello' => NULL);

var_dump( isset ($a['test') ); // TRUE
var_dump( isset ($a['foo') ); // FALSE
var_dump( isset ($a['hello') ); // FALSE

// 'hello' 等于 NULL，所以被认为是未赋值的。
// 如果想检测 NULL 键值，可以试试下边的方法。
var_dump( array_key_exists('hello', $a) ); // TRUE

<?php
$var = 0;

// 结果为 true，因为 $var 为空
if (empty($var)) { 
    echo '$var is either 0 or not set at all';
}

// 结果为 false，因为 $var 已设置
if (!isset($var)) {
    echo '$var is not set at all';
}
?>

$is_var = '';

if(isset($is_var)) {
    echo "变量存在！<br />";
} else {
    echo "变量不存在！<br />";
}

if(empty($is_var)) {
    echo "变量为空！<br />";
} else {
    echo "变量不为空！<br />";
}

?>

 extension=php_curl.dll 

<?php
// 初始化一个 cURL 对象
$curl = curl_init(); 
 
// 设置你需要抓取的URL
curl_setopt($curl, CURLOPT_URL, 'http://coolshell.cn');
 
// 设置header
curl_setopt($curl, CURLOPT_HEADER, 1);
 
// 设置cURL 参数，要求结果保存到字符串中还是输出到屏幕上。
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
 
// 运行cURL，请求网页
$data = curl_exec($curl);
 
// 关闭URL请求
curl_close($curl);
 
// 显示获得的数据
var_dump($data);

<?php
    $phoneNumber = '13912345678';
    $message = 'This message was generated by curl and php';
    $curlPost = 'pNUMBER='  . urlencode($phoneNumber) . '&MESSAGE=' . urlencode($message) . '&SUBMIT=Send';
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, 'http://www.example.com/sendSMS.php');
    curl_setopt($ch, CURLOPT_HEADER, 1);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $curlPost);
    $data = curl_exec();
    curl_close($ch);
?>

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://localhost/2.php");
curl_setopt($ch, CURLOPT_HTTPHEADER, array('X-FORWARDED-FOR:8.8.8.8', 'CLIENT-IP:8.8.8.8'));//IP
curl_setopt($ch, CURLOPT_REFERER, "http://www.111cn.net/ ");   //来路
curl_setopt($ch, CURLOPT_HEADER, 1);
$out = curl_exec($ch);
curl_close($ch);

<?php
//将utf8编码的汉字转换为unicode
function htou($c){
 $n = (ord($c[0]) & 0x1f) << 12;
 $n = (ord($c[1]) & 0x3f) << 6;
 $n = ord($c[2]) & 0x3f;
 return $n;
}

//在代码中隐藏utf8格式的字符串
function my_utf8_unicode($str) {
 $encode='';
 for($i=0;$i<strlen($str);$i ){
  if(ord(substr($str,$i,1))> 0xa0){
   $encode.='&#'.htou(substr($str,$i,3)).';';
   $i =2;
  }else{
   $encode.='&#'.ord($str[$i]).';';
  }
 }
 return $encode;
}

echo my_utf8_unicode("哈哈ABC");
?>

function getUnicode($word)
{
 // 转UTF8
 $word0 = iconv('gbk', 'utf-8', $word);
 $word1 = iconv('utf-8', 'gbk', $word0);
 $word =  ($word1 == $word) ? $word0 : $word;
 // 拆分汉字
 preg_match_all('#(?:[x00-x7F]|[xC0-xFF][x80-xBF]+)#s', $word, $array, PREG_PATTERN_ORDER);
 $return  = array();
 // 转换
 foreach ($array[0] as $cc)
 {
  $arr = str_split($cc);
  $bin_str = '';
  foreach ($arr as $value)
  {
   $bin_str .= decbin(ord($value));
  }
  $bin_str = preg_replace('/^.{4}(.{4}).{2}(.{6}).{2}(.{6})$/','$1$2$3', $bin_str);
  $return[] = '&#' . bindec($bin_str) . ';';
 }
 
 return implode('', $return);
}

$word = '一个汉字转换成Ｕｎｉｃｏｄｅ四字节编码的PHP函数。';
echo getUnicode($word);

function uni_encode ($word)
{
 $word0 = iconv('gbk', 'utf-8', $word);
 $word1 = iconv('utf-8', 'gbk', $word0);
 $word =  ($word1 == $word) ? $word0 : $word;
    $word = json_encode($word);
    $word = preg_replace_callback('/\\u(w{4})/', create_function('$hex', 'return '&#'.hexdec($hex[1]).';';'), substr($word, 1, strlen($word)-2));
    return $word;
}

function uni_decode ($uncode)
{
    $word = json_decode(preg_replace_callback('/&#(d{5});/', create_function('$dec', 'return '\u'.dechex($dec[1]);'), '"'.$uncode.'"'));
    return $word;
}

<?php

//测试时文件的编码方式要是UTF8

$str='中文a字1符';

echo strlen($str).'<br>';//14

echo mb_strlen($str,'utf8').'<br>';//6

echo mb_strlen($str,'gbk').'<br>';//8

echo mb_strlen($str,'gb2312').'<br>';//10

?> 

<?php

/**

* PHP判断字符串纯汉字 OR 纯英文 OR 汉英混合

*/
echo '<meta charset="utf-8" />';

function utf8_str($str){

$mb = mb_strlen($str,'utf-8');

$st = strlen($str);

if($st==$mb)

return '纯英文';

if($st%$mb==0 && $st%3==0)

return '纯汉字';

return '汉英混合';

}

$str = '琼台博客';

echo '字符串：<span style="color:red">'.$str.'</span>，是<span style="color:red">'.utf8_str($str).'</span>';

?>

ob_start(); 

2 内容 

3 echo ob_get_contents() ;

$cache = new Cache();

$value = $cache->get('data_key');4、写入缓存

$value = $cache->put('data_key', 'data_value');完整实例：

$cache = new Cache();

//从缓存从读取键值 $key 的数据
$values = $cache->get($key);

//如果没有缓存数据
if ($values == false) {
 //insert code here...
 //写入键值 $key 的数据
 $cache->put($key, $values);
} else {
 //insert code here...
}
Cache.class.php

<?php
class Cache {
 private $cache_path;//path for the cache
 private $cache_expire;//seconds that the cache expires

 //cache constructor, optional expiring time and cache path
 public function Cache($exp_time=3600,$path="cache/"){
  $this->cache_expire=$exp_time;
  $this->cache_path=$path;
 }

 //returns the filename for the cache
 private function fileName($key){
  return $this->cache_path.md5($key);
 }

 //creates new cache files with the given data, $key== name of the cache, data the info/values to store
 public function put($key, $data){
  $values = serialize($data);
  $filename = $this->fileName($key);
  $file = fopen($filename, 'w');
     if ($file){//able to create the file
         fwrite($file, $values);
         fclose($file);
     }
     else return false;
 }

 //returns cache for the given key
 public function get($key){
  $filename = $this->fileName($key);
  if (!file_exists($filename) || !is_readable($filename)){//can't read the cache
   return false;
  }
  if ( time() < (filemtime($filename) + $this->cache_expire) ) {//cache for the key not expired
   $file = fopen($filename, "r");// read data file
         if ($file){//able to open the file
             $data = fread($file, filesize($filename));
             fclose($file);
             return unserialize($data);//return the values
         }
         else return false;
  }
  else return false;//was expired you need to create new
  }
}
?>