What are some common pitfalls to avoid when working with header functions in PHP?

One common pitfall when working with header functions in PHP is attempting to set headers after content has already been sent to the browser. To avoid this, make sure to set headers before any output is sent to the browser. 

// Incorrect way - attempting to set headers after content has been sent
echo "Hello, World!";
header("Content-Type: text/plain");

// Correct way - set headers before any output
header("Content-Type: text/plain");
echo "Hello, World!";

Keywords

header functions PHP security caching redirect

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