Top 10 PHP Security Best Practices

1. Introduction to PHP Security

Due to the fact that PHP is the backbone of practically any website, PHP security should not be taken lightly at any cost. PHP developers, on the other hand, have the pleasure of avoiding widespread dangers like cross-site request forgery, SQL injections, and data tampering. And all of this is made possible by PHP’s built-in security capabilities, which make it easy for developers to secure their websites.

Securing web applications against all types of forged attack attempts is a web developer’s ultimate responsibility. You should design your online applications in such a way that they have no security flaws or gaps, therefore eliminating the chance of a malicious assault. In the majority of cases, developers must accept responsibility and make every attempt to detect vulnerabilities and propose fixes, if any, to the concerns present in the apps.

Web development firms have been widely using PHP as their preferred web development language to provide services such as CMS & API Development, PHP integrations, app maintenance and so forth with best end-user experience.

It is so popular that some businesses conduct bounty programmes in which they invite various security experts to assess their application from the ground up and provide important PHP security best practises.

When it comes to security, PHP is the most criticised scripting language. A sizable portion of developers and quality assurance professionals believe PHP lacks solid techniques for application security. The judgement also has some validity, given PHP is the oldest and most commonly used programming language for web application development. However, it has been a long time since PHP 5.6 had any significant security updates, and as a result, the language has certain security problems.

2. Top 10 PHP Security Best Practices

2.1 Be cautious of cross-site scripting (XSS) attacks

Cross-site scripting, or XSS, is a term that refers to your web application’s unintentional execution of remote code. For instance, when your web application receives user input and prints it immediately on the web page, an XSS attack may occur. To prevent such vulnerabilities, PHP development services often incorporate various security measures, including input validation and output encoding.

The following example contains a form that accepts user input.

<form action=”form.php” method=”post”>

<input type=”text” name=”message” value=””>

<input type=”submit” name=”submit” value=”Submit message”>

</form>

Next, we print the inputted data directly to the web page.

<?php

echo $_POST[“message”];

A rogue user can now insert JavaScript in this manner. For instance, the user can insert a script tag containing an alert function that will be executed by your web application.

<script>alert(“Hacker was here”)</script>

The preceding script element will display a straightforward alert message in the browser. This may not appear to be hazardous. However, a malevolent user might simply take sensitive personal data or the cookie of another user.

What Is the Corrective Action? To avoid a cross-site scripting attack, ensure that all user input is escaped to prevent remote code execution.

2.2 Cross-Site Request Forgery

CSRF grants hackers entire application control, allowing them to carry out any unpleasant activity. With complete control, hackers can carry out destructive actions on your website by transmitting infected code, resulting in data theft, functional alterations, and other undesirable outcomes. The exploit coerces users into changing their normal requests to damaging ones, such as unwittingly transferring funds or wiping the entire database without notification.

The CSRF attack can be launched only after you click on the hacker’s disguised harmful link. This means that if you are intelligent enough to deduce the location of the infected hidden scripts, you can quickly rule out any CSRF attack. Meanwhile, you may enhance your app’s security by utilising two protective methods, namely by include GET requests in your URL and ensuring that non-GET requests originate solely from your client-side code.

2.3 Remote File Inclusion

Remote file inclusion is the process through which remote files are included in your application. Pretty profound, eh? However, why is this a concern? Due to the fact that the external file is untrusted. It may have been modified maliciously to include code that you do not want executing in your application.

Assume that your website at www.myplace.com incorporates the script.php library from www.goodpeople.com. www.goodpeople.com is compromised one night and the file’s contents are replaced with malicious code that will destroy your programme. Then someone visits your site, you update the code, and presto! So how can you put an end to it?

Fortunately, resolving this is pretty straightforward. All you need to do is navigate to your php.ini file and verify the flags’ settings.

• allow_url_fopen – specifies if external files are permitted to be included. By default, this is set to ‘on,’ but you wish to disable it.
• allow_url_include – specifies whether the include(), require(), include_once(), and require_once() methods may make remote file references. This is disabled by default, and disabling  allow_url_fopen also disables it.

2.4 Use prepared SQL statements

A typical error is to insert user input directly into an SQL statement. This opens the door to SQL injection attacks, in which the user can circumvent the intended parameterized queries and perform.

For instance, the query below uses un-sanitized user input directly into the SQL query.

$users = mysql_query(“SELECT * FROM `users` WHERE `id`=’$_GET[id]'”);

This provides a hacker with the opportunity to circumvent the statement and query for further sensitive information, such as all users’ data. With a prepared statement, the data entered are escaped, effectively eliminating the possibility of a SQL injection attack.

Consider the following example, which makes use of a prepared statement.

$stmt = $conn->

prepare(“INSERT INTO users (firstname, lastname) VALUES (?, ?)”);

$stmt->bind_param(“ss”, $firstname, $lastname);

Take note of the bind_param function’s first parameter. This indicates to the SQL query the type of data that you are passing. The firstname and lastname inputs are both of type String in this case. This is an additional security precaution that verifies the input’s data type.

2.5 validate user input

When you check user input before accepting it via an input field, you ensure that all data is of the right kind and format.

Regular expressions (regex) are frequently used by developers to check data formats like date of birth or phone number.

Consider the following example, which verifies that the date of birth is in the format YYYY-MM-DD.

$date=”2012-09-12″;

if (preg_match(“/^[0-9]

{4}-(0[1-9]|1[0-2])

-(0[1-9]|[1-2]

[0-9]|3[0-1])$/”, $date)) {

  return true;

} else {

 return false;

}

2.6 Always Use SSL Certificates

Always utilise SSL certificates in your applications to ensure end-to-end data transfer over the internet. It is an internationally recognised standard protocol called Hypertext Transfer Protocol Secure (HTTPS) that is used to securely transport data between servers. By utilising an SSL certificate, your application gains access to a secure data transfer channel, thereby eliminating the possibility of hackers infiltrating your servers.

All major online browsers, including Google Chrome, Safari, Firefox, and Opera, advocate using an SSL certificate since it enables the transmission, receipt, and decryption of data over the internet.

2.7 Session Hijacking

Session hijacking occurs when a thief takes and uses another person’s session ID, which functions similarly to a key to a safe deposit box. When a client and a web server establish a session, PHP stores the session ID in a client-side cookie, most likely named PHPSESSID. By including the ID in the page request, you have access to the server-persisted session information.

Is it a terrible thing if someone takes a session key? And the answer is no if you are not accomplishing anything significant during that time. However, if you utilise that session to authenticate a user, it would allow some evil individual to sign on and gain access to your system. This is especially detrimental if the user is significant and possesses considerable authority.

Thus, how can these session IDs become stolen, and what can good, God-fearing people like us do about it?

Session IDs are frequently stolen via XSS attacks, thus protecting them is a win-win situation. Additionally, it is critical to update the session ID as frequently as possible. This narrows your window of opportunity for theft. You may call the session regenerate id() method from within PHP to update the session ID and alert the client.

For those who are using PHP5.2 or higher (which you are, aren’t you? ), there is a php.ini setting that prevents JavaScript from accessing the session id (session.cookie.httponly). Alternatively, you may use the function session set cookie params().

Session IDs are also susceptible on the server side if you use shared hosting services that store session data in globally accessible locations such as /tmp. Simply save your session ID in a location that only your scripts can access, either on disc or in a database, to avoid this issue.

2.8 Use URL encoding

PHP provides developers with the urlencode function, which allows them to construct valid URLs safely. According to the PHP documentation, the function is useful for encoding a string that will be used in a URL’s query section.

Consider the case when user input is utilised to generate a URL. In that situation, the urlencode function may be used to produce a secure URL.

<?php

echo ‘<a href=”mylink?user=’, urlencode($userID), ‘”>’;

?>

2.9 Deploy PHP Apps on Clouds

Hosting is the final and most critical stage in developing any online application, since you always start with local PHP servers and migrate to live servers that offer shared, cloud, or dedicated hosting. Experts usually advocate cloud hosting providers such as DigitalOcean, Linode, and AWS. They are quick, secure, and suitable for any type of website or application. They always offer a secure layer to protect online applications from DDOS, brute force, and phishing assaults.

To deploy PHP applications on cloud servers, you must have strong Linux expertise in order to construct robust web stacks such as LAMP or LEMP, which frequently requires additional time and money for Linux specialists. Rather than that, Cloudways’ managed PHP and MySQL hosting platform enables you to easily install Thunderstack servers on the aforementioned cloud providers with a few clicks. Thunderstack protects your PHP application against a variety of harmful threats and ensures optimal performance.

2.10 Regularly Update your PHP versions

PHP 7.4.8 is the stable release as of July 9, 2020. It is critical to update your PHP version on a regular basis since newer versions frequently include patches for known security vulnerabilities. If you do not upgrade to the newest stable edition of PHP, hackers will be able to exploit known security flaws in previous releases.

Additionally, PHP allows you to test a preview release. This release is currently 8.0.0 Beta 2. Security consultants, on the other hand, caution businesses against testing preview versions since they may still include undisclosed security issues.

3. An outline of PHP security

Finally, as a PHP developer, you are accountable not just for providing the needed business logic but also for guaranteeing its and your code’s security.

The primary takeaway from this article is the importance of validating user input. Unvalidated user input is frequently the source of a security vulnerability. Consider security problems such as remote file inclusion, URL encoding, or a cross-site scripting (XSS) attack. Each of these occurs as a result of invalidated user input.