Web Security

How to Secure a PHP Website: Top OWASP Vulnerabilities and Defenses

A practical security audit guide covering CSRF tokens, XSS output encoding, secure session flags, clickjacking defenses, and security headers.

Marcus Thorne Written by Marcus Thorne
Published: 10/06/2026 8 min read

Defense in Depth for Modern PHP

Security is not a single plugin—it is a comprehensive layered architecture. Secure PHP applications must address the primary threat vectors documented by OWASP:

  • Cross-Site Scripting (XSS): Always escape output when rendering dynamic variables in HTML using htmlspecialchars($var, ENT_QUOTES, 'UTF-8').
  • Cross-Site Request Forgery (CSRF): Validate cryptographically secure tokens on every state-changing POST/PUT request.
  • Security Headers: Deliver X-Content-Type-Options: nosniff, X-Frame-Options: SAMEORIGIN, and a tailored Content-Security-Policy.
Marcus Thorne

Marcus Thorne

Head of Technology & Web Engineering

Marcus is a full-stack engineer and educator who has architected fintech payment gateways, secure authentication engines, and performant data pipelines using modern PHP and MySQL.

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