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How to prevent SQL injection in PHP?


Prevent SQL injection in PHP: As we all know that SQL injections are very often in any PHP application or site, the issue is that they can be pretty harmful too. These SQL injections mainly occur due to the faults in backend programming. In general, SQL injection refers to an injection attack where an attacker can execute arbitrary SQL statements. This is done by tricking a web application in processing an attacker’s input as part of an SQL statement. In this article, we will get to know the different methods on how to prevent SQL injection in PHP.

Even though, PHP is one of the programming languages which are developed with built in web development capabilities the web developers cannot write large web applications directly. The programmers can embed the code written in this popular server-side programming language seamlessly into HTML code through the Script tag. Unlike the other programming languages, PHP does not emphasize on code readability and maintainability.

SQL Injection in PHP

An SQL Injection vulnerability may affect any website or web application that uses an SQL database such as MySQL, Oracle, SQL Server, or others. Criminals may use it to gain unauthorized access to your sensitive data: customer information, personal data, trade secrets, intellectual property, and more. In order to make a SQL injection attack, an attacker firstly need to find vulnerable user inputs within the web page or the web application. There are several types of SQL Injection attacks: in-band SQLi (using database errors or UNION commands), blind SQLi, and out-of-band SQLi.

SQL injections can be prevented by using the prepared statements in PHP. Prepared Statements use bound parameters and do not combine variables with SQL strings, making it impossible for an attacker to modify the SQL statement. Prepared Statements combine the variable with the compiled SQL statement so that the SQL and the variables are sent separately. The variables are then interpreted as mere strings and not part of the SQL statement.

By using the SQLi prepared statements you can prevent the SQL injection. Scroll down below to learn in detail on how you can prevent the SQL injecton using prepared statements.

SQL Injection

  1. Create the mySQLi SELECT query

    Firstly, you need to create the mySQLi SELECT query. You can use the code below to select data from a table using mySQLi prepared statements. How to prevent SQL injection in PHP

  2. Create the mySQLi INSERT query

    You can use the code below to INSERT data into a table using my SQLi prepared statements. Create the mySQLi insertion query to prevent SQL injection

  3. Create the mySQLi UPDATE Query

    You can use the code below to UPDATE data in a table using mySQLi Prepared Statements. Update mySQLi to prevent SQL injection

  4. Create the mySQLi DELETE query

    In the below depicted picture you can find how to delete DATA from a table using mySQLi prepared statements.Delete data from mySQLi to prevent SQL injection

Another way you use to solve the SQL injection problem is the TDD.


TDD is nothing but a test driven development in which you write the test first and code later to pass the test. This approach ensures that the number of bugs must be solved during development. The process of a TDD is as follows,

  1. Write a Test
  2. Run a Test
  3. Write the code
  4. Run the test again and see it pass
  5. Refacto

In the above process, we can clearly see that we first write the test and then pass the code from it. If the test passes then the cycle will go in a loop. Here is a visual representation of the TDD cycle.

TDD Cycle

Solutions to SQL injection vulnerabilities

Although SQL injection is a complicated topic, in this article we will go through two set of solutions for SQL injection vulnerabilities.

Solution 1: Make few changes from the previous code.

Make few changes to previous code to prevent SQL injection
Make changes to previous code

Through the above statement, str_replace() function will replace all characters in the string. Now you will use the function as follows:

Str() replace function replaces all the characters in the string

Solution 2: The other solution to prevent SQL injection is through the prepared statements. The detailed explanation of preventing SQL injection is as mentioned above.

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Advantages of Prepared Statements

The main advantages of prepared statements are as follows,

  1. Reduces the parsing time as the query is executed once but can be executed multiple times with the same parameters.
  2. Bound parameters reduce the bandwidth to the server because the whole query is not sent every time but the parameters are sending.
  3. Bound Parameters reduces the bandwidth as the whole query is not sent every time but parameters are sent.


Here are some top 3 FAQ’s in regard to the PHP and SQL injection. These FAQ’s might clear up your mind in regard to specific doubts if any. Scroll down below to know more,

What is Blind SQL injection?

Blind SQL (Structured Query Language) injection is a type of SQL Injection attack that asks the database true or false questions and determines the answer based on the response of the application. This makes exploiting the SQL Injection vulnerability more difficult, but not impossible.

Is SQL injection still a threat?

Yes, SQL injections are still a threat. There are always new vulnerabilities found with these types of things. Here are some reasons why injections can still be thought of as a threat. It’s an easy attack, only one computer is required when others take many computers to attack.

What is SQL mapping?

A SQL Map enables you to publish data service functions as SQL objects (which are created when you specify the mapping). Using SQL Maps, you can expose data services modeled in Oracle Data Service Integrator as relational data sources.

To conclude: Hence, through this article, we got to learn about the prevention techniques and solutions for SQL injection. If you have any queries in regard to the above content, do quote them in the comment section below. Also, comment your views on the topic and do share the content. For some more of interest tech articles visit and delve into amazing content on the web.

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