Looking for the equivalent of this in PHP?
Check out htmlspecialchars and htmlentities.
This tool converts special HTML characters in a block of text into sequences that render in HTML as those characters. The script runs inside your browser, and does not transmit your input off your computer.
Its default function is to prepare a block of HTML code so that a web page can display the code itself instead of rendering it. It can also be used to encode a string of text that you plan to insert into an attribute on an HTML tag.
Paste some text into the “Raw” field below, and click “Encode.” Then copy the result out of the “Encoded” field. To see how the encoded text will appear when rendered on an HTML page, you can click the “Render HTML” button.