1.不要使用相对路径
常常会看到:
require_once('../../lib/some_class.php');另一问题, 当定时任务运行该脚本, 它的上级目录可能就不是工作目录了。 因此最佳选择是使用绝对路径:
view sourceprint? define('ROOT' , '/var/www/project/'); require_once(ROOT . '../../lib/some_class.php'); //rest of the code
//suppose your script is /var/www/project/index.php //Then __FILE__ will always have that full path. define('ROOT' , pathinfo(__FILE__, PATHINFO_DIRNAME)); require_once(ROOT . '../../lib/some_class.php'); //rest of the code
require_once('lib/Database.php'); require_once('lib/Mail.php'); require_once('helpers/utitlity_functions.php');function load_class($class_name) { //path to the class file $path = ROOT . '/lib/' . $class_name . '.php'); require_once( $path ); } load_class('Database'); load_class('Mail');有什么不一样吗? 该代码更具可读性。 將来你可以按需扩展该函数, 如:
function load_class($class_name) { //path to the class file $path = ROOT . '/lib/' . $class_name . '.php'); if(file_exists($path)) { require_once( $path ); } }还可做得更多: 为同样文件查找多个目录。 能很容易的改变放置类文件的目录, 无须在代码各处一一修改。 可使用类似的函数加载文件, 如html内容.
3. 为应用保留调试代码在开发环境中, 我们打印数据库查询语句, 转存有问题的变量值, 而一旦问题解决, 我们注释或删除它们. 然而更好的做法是保留调试代码。 在开发环境中, 你可以:
define('ENVIRONMENT' , 'development'); if(! $db->query( $query ) { if(ENVIRONMENT == 'development') { echo "$query failed"; } else { echo "Database error. Please contact administrator"; } }define('ENVIRONMENT' , 'production'); if(! $db->query( $query ) { if(ENVIRONMENT == 'development') { echo "$query failed"; } else { echo "Database error. Please contact administrator"; } }system, exec, passthru, shell_exec 这4个函数可用于执行系统命令. 每个的行为都有细微差别. 问题在于, 当在共享主机中, 某些函数可能被选择性的禁用. 大多数新手趋于每次首先检查哪个函数可用, 然而再使用它。 更好的方案是封成函数一个可跨平台的函数.
/** Method to execute a command in the terminal Uses : 1. system 2. passthru 3. exec 4. shell_exec */ function terminal($command) { //system if(function_exists('system')) { ob_start(); system($command , $return_var); $output = ob_get_contents(); ob_end_clean(); } //passthru else if(function_exists('passthru')) { ob_start(); passthru($command , $return_var); $output = ob_get_contents(); ob_end_clean(); } //exec else if(function_exists('exec')) { exec($command , $output , $return_var); $output = implode("\n" , $output); } //shell_exec else if(function_exists('shell_exec')) { $output = shell_exec($command) ; } else { $output = 'Command execution not possible on this system'; $return_var = 1; }return array('output' => $output , 'status' => $return_var); } terminal('ls');function add_to_cart($item_id , $qty) { $_SESSION['cart']['item_id'] = $qty; }add_to_cart( 'IPHONE3' , 2 );
function add_to_cart($item_id , $qty) { if(!is_array($item_id)) { $_SESSION['cart']['item_id'] = $qty; } else { foreach($item_id as $i_id => $qty) { $_SESSION['cart']['i_id'] = $qty; } } } add_to_cart( 'IPHONE3' , 2 ); add_to_cart( array('IPHONE3' => 2 , 'IPAD' => 5) );<?php echo "Hello"; //Now dont close this tag
<?php class super_class { function super_function() { //super code } } ?>//super extra character after the closing tag
index.php require_once('super_class.php'); //echo an image or pdf , or set the cookies or session data这样, 你將会得到一个 Headers already send error. 为什么? 因为 “super extra character” 已经被输出了. 现在你得开始调试啦. 这会花费大量时间寻找 super extra 的位置。 因此, 养成省略关闭符的习惯:
<?php class super_class { function super_function() { //super code } } //No closing tagfunction print_header() { echo "<div id='header'>Site Log and Login links</div>"; } function print_footer() { echo "<div id='footer'>Site was made by me</div>"; } print_header(); for($i = 0 ; $i < 100; $i++) { echo "I is : $i '; }print_footer();function print_header() { $o = "<div id='header'>Site Log and Login links</div>"; return $o; }function print_footer() { $o = "<div id='footer'>Site was made by me</div>"; return $o; }echo print_header(); for($i = 0 ; $i < 100; $i++) { echo "I is : $i '; } echo print_footer();$xml = '<?xml version="1.0" encoding="utf-8" standalone="yes"?>'; $xml = "<response> <code>0</code> </response>";//Send xml data echo $xml;
$xml = '<?xml version="1.0" encoding="utf-8" standalone="yes"?>'; $xml = "<response> <code>0</code> </response>"; //Send xml data header("content-type: text/xml"); echo $xml;JavaScriptheader("content-type: application/x-javascript"); echo "var a = 10"; CSSheader("content-type: text/css"); echo "#div id { background:#000; }";//Attempt to connect to database $c = mysqli_connect($this->host , $this->username, $this->password); //Check connection validity if (!$c) { die ("Could not connect to the database host: ". mysqli_connect_error()); } //Set the character set of the connectionif(!mysqli_set_charset ( $c , 'UTF8' )) { die('mysqli_set_charset() failed'); }$value = htmlentities($this->value , ENT_QUOTES , CHARSET);
$images = array( 'myself.png' , 'friends.png' , 'colleagues.png' );$js_code = '';foreach($images as $image){$js_code .= "'$image' ,";}$js_code = 'var images = [' . $js_code . ']; ';echo $js_code;//Output is var images = ['myself.png' ,'friends.png' ,'colleagues.png' ,]; 更聪明的做法, 使用 json_encode: $images = array( 'myself.png' , 'friends.png' , 'colleagues.png' );$js_code = 'var images = ' . json_encode($images); echo $js_code;//Output is : var images = ["myself.png","friends.png","colleagues.png"]优雅乎?
13. 写文件前, 检查目录写权限 写或保存文件前, 确保目录是可写的, 假如不可写, 输出错误信息. 这会节约你很多调试时间. linux系统中, 需要处理权限, 目录权限不当会导致很多很多的问题, 文件也有可能无法读取等等. 确保你的应用足够智能, 输出某些重要信息.
$contents = "All the content";$file_path = "/var/www/project/content.txt"; file_put_contents($file_path , $contents);
这大体上正确. 但有些间接的问题. file_put_contents 可能会由于几个原因失败:
>>父目录不存在 >>目录存在, 但不可写 >>文件被写锁住? 所以写文件前做明确的检查更好.$contents = "All the content"; $dir = '/var/www/project'; $file_path = $dir . "/content.txt"; if(is_writable($dir)) { file_put_contents($file_path , $contents); } else { die("Directory $dir is not writable, or does not exist. Please check"); }// Read and write for owner, read for everybody else chmod("/somedir/somefile", 0644); // Everything for owner, read and execute for others chmod("/somedir/somefile", 0755);
if($_POST['submit'] == 'Save') { //Save the things }上面大多数情况正确, 除了应用是多语言的. ‘Save’ 可能代表其它含义. 你怎么区分它们呢. 因此, 不要依赖于submit按钮的值.
if( $_SERVER['REQUEST_METHOD'] == 'POST' and isset($_POST['submit']) ) { //Save the things }//Delay for some time function delay() { $sync_delay = get_option('sync_delay'); echo "Delaying for $sync_delay seconds..."; sleep($sync_delay); echo "Done "; }//Delay for some time function delay() { static $sync_delay = null; if($sync_delay == null) { $sync_delay = get_option('sync_delay'); } echo "Delaying for $sync_delay seconds..."; sleep($sync_delay); echo "Done "; }
$_SESSION['username'] = $username; $username = $_SESSION['username'];
define('APP_ID' , 'abc_corp_ecommerce'); //Function to get a session variable function session_get($key) { $k = APP_ID . '.' . $key; if(isset($_SESSION[$k])) { return $_SESSION[$k]; } return false; } //Function set the session variable function session_set($key , $value) { $k = APP_ID . '.' . $key; $_SESSION[$k] = $value; return true; }function utility_a() { //This function does a utility thing like string processing }function utility_b() { //This function does nother utility thing like database processing } function utility_c() { //This function is ... }class Utility {public static function utility_a(){}public static function utility_b() { }public static function utility_c() { } }//and call them as $a = Utility::utility_a(); $b = Utility::utility_b();<span style="color:#333333;font-family:''Helvetica, Arial, sans-serif'';">if($a == true) $a_count++;</span>
这绝对WASTE。 写成:
<span style="color:#333333;font-family:''Helvetica, Arial, sans-serif'';">if($a == true) { $a_count++; }</span>
foreach($arr as $c => $v) { $arr[$c] = trim($v); }$arr = array_map('trim' , $arr);$amount = intval( $_GET['amount'] ); $rate = (int) $_GET['rate'];
$db_records_in_array_format; //This is a big array holding 1000 rows from a table each having 20 columns , every row is atleast 100 bytes , so total 1000 * 20 * 100 = 2MB$cc = $db_records_in_array_format; //2MB moresome_function($cc); //Another 2MB ?
当导入或导出csv文件时, 常常会这么做。 不要认为上面的代码会经常因内存限制导致脚本崩溃. 对于小的变量是没问题的, 但处理大数组的时候就必须避免.
确保通过引用传递, 或存储在类变量中:$a = get_large_array(); pass_to_function(&$a);
class A { function first() { $this->a = get_large_array(); $this->pass_to_function(); } function pass_to_function() { //process $this->a } }
function add_to_cart() {$db = new Database(); $db->query("INSERT INTO cart ....."); } function empty_cart() {$db = new Database(); $db->query("DELETE FROM cart ....."); }<span style="color:#333333;font-family:''Helvetica, Arial, sans-serif'';">$query = "INSERT INTO users(name , email , address , phone) VALUES('$name' , '$email' , '$address' , '$phone')"; $db->query($query); //call to mysqli_query()</span><span style="color:#333333;font-family:''Helvetica, Arial, sans-serif'';">function insert_record($table_name , $data) { foreach($data as $key => $value) { //mysqli_real_escape_string $data[$key] = $db->mres($value); } $fields = implode(',' , array_keys($data)); $values = "'" . implode("','" , array_values($data)) . "'"; //Final query $query = "INSERT INTO {$table}($fields) VALUES($values)"; return $db->query($query);} $data = array('name' => $name , 'email' => $email , 'address' => $address , 'phone' => $phone); insert_record('users' , $data);</span>看到了吗? 这样会更易读和扩展. record_data 函数小心的处理了转义。 最大的优点是数据被预处理为一个数组, 任何语法错误都会被捕获。 该函数应该定义在某个database类中, 你可以像 $db->insert_record这样调用。 查看本文, 看看怎样让你处理数据库更容易。 类似的也可以编写update,select,delete方法. 试试吧.
27. 將数据库生成的内容缓存到静态文件中 如果所有的内容都是从数据库获取的, 它们应该被缓存. 一旦生成了, 就將它们保存在临时文件中. 下次请求该页面时, 可直接从缓存中取, 不用再查数据库. 好处: >>节约php处理页面的时间, 执行更快 >>更少的数据库查询意味着更少的mysql连接开销 28. 在数据库中保存session 基于文件的session策略会有很多限制. 使用基于文件的session不能扩展到集群中, 因为session保存在单个服务器中. 但数据库可被多个服务器访问, 这样就可以解决问题. 在数据库中保存session数据, 还有更多好处: >>处理username重复登录问题. 同个username不能在两个地方同时登录. >>能更准备的查询在线用户状态. 29. 避免使用全局变量 >>使用 defines/constants >>使用函数获取值 >>使用类并通过$this访问 30. 在head中使用base标签 没听说过? 请看下面:
<head> <base href="http://www.domain.com/store/"> </head> <body> <img src="happy.jpg" / alt="【精品推荐】高质量PHP代码的50个实用技巧" > </body> </html>
<a href="home.php">Home</a> <a href="products/ipad.php">Ipad</a>
<span style="max-width:90%"Helvetica, Arial, sans-serif'';"><a href="../home.php">Home</a> <a href="ipad.php">Ipad</a></span>
因为目录不一样. 有这么多不同版本的导航菜单要维护, 很糟糕啊。 因此, 请使用base标签.