EASYTUTORGUIDEPHP • PHP 8.5.10

Web Security: XSS, CSRF, SQL Injection

Chapter 48 of 60 • beginner to advanced • code example for every topic

5 topics5 code examples10 Q&A

48.1 Threat Model 48.2 Input Validation 48.3 Authentication/Authorization 48.4 Secret Handling 48.5 Secure Defaults

48.1 Threat Model

This topic teaches Threat Model as part of Web Security: XSS, CSRF, SQL Injection. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

<?php
// Threat Model
$value = 42;
echo "PHP example: $value\n";

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Threat Model. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

48.2 Input Validation

This topic teaches Input Validation as part of Web Security: XSS, CSRF, SQL Injection. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

<?php
// Input Validation
$value = 42;
echo "PHP example: $value\n";

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Input Validation. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

48.3 Authentication/Authorization

This topic teaches Authentication/Authorization as part of Web Security: XSS, CSRF, SQL Injection. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

<?php
$hash=password_hash("correct horse battery staple",PASSWORD_DEFAULT);
var_dump(password_verify("correct horse battery staple",$hash));

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Authentication/Authorization. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

48.4 Secret Handling

This topic teaches Secret Handling as part of Web Security: XSS, CSRF, SQL Injection. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

<?php
// Secret Handling
$value = 42;
echo "PHP example: $value\n";

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Secret Handling. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.

48.5 Secure Defaults

This topic teaches Secure Defaults as part of Web Security: XSS, CSRF, SQL Injection. Learn the purpose first, then inspect the syntax and test it with small inputs before using it in production.

Code example

<?php
// Secure Defaults
$value = 42;
echo "PHP example: $value\n";

Step-by-step explanation

Identify the values, objects, tables, or resources used by the example.
Read each statement in execution order.
Predict what the program or query should produce.
Run it in a safe local/test environment.
Change one input and explain the new result.

Expected output/result

You should see a small result that demonstrates Secure Defaults. Exact formatting can differ by runtime, client, database state, operating system, or tool version.

Common mistakes

Watch for invalid input, unchecked errors, incorrect type assumptions, missing cleanup, unsafe permissions, injection risks, or code/query logic that handles only the happy path.

Practice exercise

Rebuild this example with your own data. Add one edge case, predict the result before running it, and explain why the final result is correct.