PHP项目小知识点应用(持续更新中)

//几个有效的$_SERVER信息
$_SERVER['HTTP_USER_AGENT']; //内核信息
$_SERVER['HTTP_REFERER'];    //来源信息
$_SERVER['SERVER_ADDR'];     //服务端IP
$_SERVER['REMOTE_ADDR'];     //客户端IP

$str = "https://www.baidu.com/";
if(strpos($str,'http') !== false){
  echo "存在";
}else{
  echo "不存在";
}

//判断是否为微信浏览器
function is_weixin(){ 
    if(strpos($_SERVER['HTTP_USER_AGENT'], 'MicroMessenger') !== false){
        return true;
    }    
    return false;
}

//来源不是本站点，返回第一步
if(strpos($_SERVER['HTTP_REFERER'], WEB_URL)===false) {
    header('Location:/');
}

//判断访问设备是iso还是android系统
if(strpos($_SERVER['HTTP_USER_AGENT'], 'iPhone')||strpos($_SERVER['HTTP_USER_AGENT'], 'iPad')){
    echo 'systerm is IOS';
}else if(strpos($_SERVER['HTTP_USER_AGENT'], 'Android')){
    echo 'systerm is Android';
}

//手机号码中间隐藏
$mobile = '18812345678';
echo preg_replace('/(\d{3})(\d{4})/',"$1****", $mobile);

//字符串拼接
$cost_point = 108;
$scale = 48.6;
$desc = sprintf('我已上够%s节课，超过了全国%s的用户，你也快来挑战上课记录吧！', $cost_point, $scale . '%');

/**
 * str_replace函数详解
 * str_replace($search , $replace , $subject [, int &$count ] )
 * 参数说明：$search要被搜索替换的字符串，$replace要替换搜索的字符串，$subject操作的字符串，&$count替换次数
 * $search和$replace都为数组
 * 示例：str_replace(array("a", "p"), array("apple", "pear"), "I like eat apple.");
 * 说明：在$subject中将$search的各元素值依次分别替换为$replace的各元素值。
 * 返回："I like eapearpearlet apearpearlepearpearle."
 */
$str = str_replace(array("a", "p"), array("apple", "pear"), "I like eat apple.");
//var_dump($str);die; //I like eapearpearlet apearpearlepearpearle.

//文件读取
$str = file_get_contents("filename.txt");
$newStr = str_replace(array("\n","\r",',,'),array(',', ',', ','),$str);
//文件写入
file_put_contents ('./filename.txt', "1222\n",FILE_APPEND); //追加写入
file_put_contents ('./filename.txt', "1222\n"); //替换写入