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PHP · LESSON 11

Form Validation and Input Sanitization

By Ratan Updated: 16 Oct 2026

Sanitize user inputs using filter_input(), htmlspecialchars(), and prevent Cross-Site Scripting (XSS).

Level: Beginner to Advanced
Duration: ~60 Mins Deep-Dive

1. Why Server-Side Validation is Mandatory

While HTML5 attributes like required and type="email" provide immediate UX feedback, client-side validation can be effortlessly bypassed using DevTools, cURL, or Postman. The server must validate and sanitize all incoming payloads.

2. Sanitization vs Validation

  • Sanitization: Cleanses input by stripping unauthorized characters, whitespace, or scripts.
  • Validation: Checks whether input conforms to expected criteria (e.g., length, numeric bounds, valid email pattern).

3. Using PHP filter_var()

";
} else {
    echo "Invalid email format.
"; } // Validating Integer with Range $age = 22; $intOptions = ["options" => ["min_range" => 18, "max_range" => 65]]; if (filter_var($age, FILTER_VALIDATE_INT, $intOptions)) { echo "Age is within valid adult range.
"; } // Validating URL $website = "https://onlinecbt.in"; if (filter_var($website, FILTER_VALIDATE_URL)) { echo "Valid web URL.
"; }

4. Structured Form Validation Pattern

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