How to protect your website from malicious user input using PHP | utink blog Skip to content

How to protect your website from malicious user input using PHP

Posted by Kevin - utink web design on
A quick and simple way to make user input safe & secure would be to use the PHP 'htmlentities()' function... (see also the htmlspecialchars() function)

This converts the following:
  • < becomes &lt
  • > becomes &gt
  • " becomes &quote
  •  ' becomes &#039 

example:
"Your site is about to be nobbled, lol! <script type='text/javascript'> window.location = 'http://www.anotherwebsite.com.au/'; </script>"
becomes:
&quote;Your site is about to be nobbled, lol! &lt;script type=&#039&;text/javascript&#039;&gt; window.location = &#039;http://www.anotherwebsite.com.au/&#039;; &lt;/script&gt;&quote;

Every echo or print command should use the htmlentities (or htmlspecialchars) function. This solution is by no means exhaustive and there are other ways to make your website secure which are beyond the scope of this blog. Note: The htmlentities function produces highly sanitized text that could make it difficult for other parts of your code to decipher eg. SQL injection. For this reason you might use the html_entity_decode function which reverses the htmlentities outcome, or you could use other forms of sanitizing for your user inputs.

Further Reading:
htmlentities()
htmlspecialchars()
html_entity_decode()

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