How to make a highly secure PHP website, summary of security issues that need to be paid attention to when making a website

Everyone knows that PHP is currently the most popular web application programming language. But like other scripting languages, PHP also has several dangerous security holes. So in this tutorial, we'll take a look at a few practical tips to help you avoid some common PHP security issues.

Tip 1: Use appropriate error reports

Generally during the development process, many programmers always forget to make program error reports, which is extremely Big mistake, because proper error reporting is not only the best debugging tool, but also an excellent security vulnerability detection tool, which allows you to find as many problems as possible before you actually put the application online.
Of course there are many ways to enable error reporting. For example, in php.in Configuration file you can set to enable

Start error reporting at runtime
error_reporting(E_ALL);

Disable error reporting
error_reporting(0);

Tip 2: Not using PHP’s Weak attribute

There are several PHP properties that need to be set to OFF. Generally, they exist in PHP4, but their use is not recommended in PHP5. Especially in PHP6, these attributes were removed.

Register global variables
When register_globals is set to ON, it is equivalent to setting Environment, GET, POST, COOKIE or Server variables are defined as global variables. At this time, you don't need to write $_POST['username'] to get the form variable 'username'. You only need '$username' to get this variable.
Then you must be thinking that since setting register_globals to ON has such convenient benefits, why not use it? Because if you do this it will bring about a lot of security issues, and it may also conflict with local variable names.
For example, take a look at the following code:

if( !empty( $_POST[‘username'] ) && $_POST[‘username'] == ‘test123′ && !empty( $_POST[‘password'] ) && $_POST[‘password'] == “pass123″ )
{
$access = true;
}

If register_globals is set to ON during operation, then the user only needs to transmit access=1 in a query string to get the PHP script running Anything anymore.
Disable global variables in .htaccess

php_flag register_globals 0

Disable global variables in php.ini

register_globals = Off

Disable magic like magic_quotes_gpc, magic_quotes_runtime, magic_quotes_sybase Quotes
Set in .htaccess file

php_flag magic_quotes_gpc 0
php_flag magic_quotes_runtime 0

Set in php.ini

magic_quotes_gpc = Off
magic_quotes_runtime = Off
magic_quotes_sybase = Off

Tip 3: Validate user input

Of course you You can also validate user input. First you must know the data type you expect the user to input. In this way, you can be prepared on the browser side to prevent users from malicious attacks on you.

Tip 4: Avoid cross-site scripting attacks by users

In web applications, it is simple to accept user input in the form and then feedback the results. When accepting user input, it would be very dangerous to allow HTML format input, because this would also allow JavaScript to intrude in unpredictable ways and execute directly. Even if there is only one such vulnerability, cookie data may be stolen and the user's account may be stolen.

Tip 5: Prevent SQL injection attacks

PHP basically does not provide any tools to protect your database, so when you connect to the database, You can use the following mysqli_real_escape_string function.

$username = mysqli_real_escape_string( $GET[‘username'] );
mysql_query( “SELECT * FROM tbl_employee WHERE username = '”.$username.“‘”);

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