PHP入门

从表面上看，很容易误解empty()函数是判断字符串是否为空的函数，其实并不是，我也因此吃了很多亏。

empty()函数是用来测试变量是否已经配置。若变量已存在、非空字符串或者非零，则返回 false 值；反之返回 true值。所以，当字符串的值为0时，也返回true，就是执行empty内部的语句。这就是陷阱。

下面给大家看看我的数据库结构吧：数据库的名字为：fa_category

     我们使用一个parentid字段来记录父节点的id，如果parentid为0，则为root。不多说，我们看看代码怎么写吧。我们要实现的功能就是如图片所示：

1.对于一般的变量，把该变量变成php语言的格式，写到文件中，用时只要include这个文件就相当于加载了cache了；
2.对于array型的变量，把array转化为php语言定义array的字符串，写到文件中，用时也只要include就相当于加载了cache了；
3.缓存cache时间上的控制，通过获取缓存文件的创建时间和现在的时间进行对比，如果没有到更新时间，直接读取缓存，如果到了更新时间，查询数据库，

先看一个php与mysql数据库的无限分类

建立数据库 :
id,fid,fname(id和fid都必需是数字类型而且fid的默认值一定要设成0;

SQLite的时间函数跟Python的时间函数有些许差别，所以稍做记录，供自己以后查询。
    网上有将SQLite官方WIKI内容翻译成中文的文章，大家有兴趣可以搜索一下，我这里单纯记录一下个人比较常用的一些内容。

简单的mysql数据表结构

CREATE TABLE messages
(
msg_id INT PRIMARY KEY AUTO_INCREMENT,
message VARCHAR(150)
);

<?php
// Adam's Custom PHP MySQL Pagination Tutorial and Script
// You have to put your mysql connection data and alter the SQL queries(both queries)
// This script is in tutorial form and is accompanied by the following video:
mysql_connect("DB_Host_Here","DB_Username_Here","DB_Password_Here") or die (mysql_error());
mysql_select_db("DB_Name_Here") or die (mysql_error());
//////////////  QUERY THE MEMBER DATA INITIALLY LIKE YOU NORMALLY WOULD
$sql = mysql_query("SELECT id, firstname, country FROM myTable ORDER BY id ASC");
//////////////////////////////////// Adam's Pagination Logic ////////////////////////////////////////////////////////////////////////
$nr = mysql_num_rows($sql); // Get total of Num rows from the database query
if (isset($_GET['pn'])) { // Get pn from URL vars if it is present
    $pn = preg_replace('#[^0-9]#i', '', $_GET['pn']); // filter everything but numbers for security(new)
    //$pn = ereg_replace("[^0-9]", "", $_GET['pn']); // filter everything but numbers for security(deprecated)
} else { // If the pn URL variable is not present force it to be value of page number 1
    $pn = 1;
}
//This is where we set how many database items to show on each page
$itemsPerPage = 10;
// Get the value of the last page in the pagination result set
$lastPage = ceil($nr / $itemsPerPage);
// Be sure URL variable $pn(page number) is no lower than page 1 and no higher than $lastpage
if ($pn < 1) { // If it is less than 1
    $pn = 1; // force if to be 1
} else if ($pn > $lastPage) { // if it is greater than $lastpage
    $pn = $lastPage; // force it to be $lastpage's value
}
// This creates the numbers to click in between the next and back buttons
// This section is explained well in the video that accompanies this script
$centerPages = "";
$sub1 = $pn - 1;
$sub2 = $pn - 2;
$add1 = $pn + 1;
$add2 = $pn + 2;
if ($pn == 1) {
    $centerPages .= '&nbsp; <span class="pagNumActive">' . $pn . '</span> &nbsp;';
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $add1 . '">' . $add1 . '</a> &nbsp;';
} else if ($pn == $lastPage) {
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $sub1 . '">' . $sub1 . '</a> &nbsp;';
    $centerPages .= '&nbsp; <span class="pagNumActive">' . $pn . '</span> &nbsp;';
} else if ($pn > 2 && $pn < ($lastPage - 1)) {
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $sub2 . '">' . $sub2 . '</a> &nbsp;';
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $sub1 . '">' . $sub1 . '</a> &nbsp;';
    $centerPages .= '&nbsp; <span class="pagNumActive">' . $pn . '</span> &nbsp;';
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $add1 . '">' . $add1 . '</a> &nbsp;';
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $add2 . '">' . $add2 . '</a> &nbsp;';
} else if ($pn > 1 && $pn < $lastPage) {
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $sub1 . '">' . $sub1 . '</a> &nbsp;';
    $centerPages .= '&nbsp; <span class="pagNumActive">' . $pn . '</span> &nbsp;';
    $centerPages .= '&nbsp; <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $add1 . '">' . $add1 . '</a> &nbsp;';
}
// This line sets the "LIMIT" range... the 2 values we place to choose a range of rows from database in our query
$limit = 'LIMIT ' .($pn - 1) * $itemsPerPage .',' .$itemsPerPage;
// Now we are going to run the same query as above but this time add $limit onto the end of the SQL syntax
// $sql2 is what we will use to fuel our while loop statement below
$sql2 = mysql_query("SELECT id, firstname, country FROM myTable ORDER BY id ASC $limit");
//////////////////////////////// END Adam's Pagination Logic ////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////// Adam's Pagination Display Setup /////////////////////////////////////////////////////////////////////
$paginationDisplay = ""; // Initialize the pagination output variable
// This code runs only if the last page variable is ot equal to 1, if it is only 1 page we require no paginated links to display
if ($lastPage != "1"){
    // This shows the user what page they are on, and the total number of pages
    $paginationDisplay .= 'Page <strong>' . $pn . '</strong> of ' . $lastPage. '&nbsp;  &nbsp;  &nbsp; ';
    // If we are not on page 1 we can place the Back button
    if ($pn != 1) {
        $previous = $pn - 1;
        $paginationDisplay .=  '&nbsp;  <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $previous . '"> Back</a> ';
    }
    // Lay in the clickable numbers display here between the Back and Next links
    $paginationDisplay .= '<span class="paginationNumbers">' . $centerPages . '</span>';
    // If we are not on the very last page we can place the Next button
    if ($pn != $lastPage) {
        $nextPage = $pn + 1;
        $paginationDisplay .=  '&nbsp;  <a href="' . $_SERVER['PHP_SELF'] . '?pn=' . $nextPage . '"> Next</a> ';
    }
}
///////////////////////////////////// END Adam's Pagination Display Setup ///////////////////////////////////////////////////////////////////////////
// Build the Output Section Here
$outputList = '';
while($row = mysql_fetch_array($sql2)){

curl默认是未被启用的，启用方法。

启用 cURL 设置

isset  — 检测变量是否设置
PHP isset() 用于检测一个或多个变量是否设置，如果被检测的变量存在则返回 TRUE，否则返回 FALSE。

例子：

方法一，在php页面设置时区

在页面最前面加上下面应用一种都是可以的

<?php
//数据库处理类
class db
{
    //SQL执行后的数据保存变量;
    var $db;
    //读取或设置当前数据的位置
    var $position=0;
    //执行SQL语句并把结果保存为db变量中;

方法一：

用serialize写入，再用unserialize输出