How can mixing different languages in PHP code affect readability and maintenance?

Mixing different languages in PHP code can make the code harder to read and maintain because developers may need to switch between languages, which can lead to confusion and errors. To improve readability and maintenance, it's best to stick to one language within the codebase.

// Bad example: Mixing different languages in PHP code
$hello = "Hello";
echo "$hello, world!"; // Using English in PHP code

// Good example: Using only PHP in the code
$hello = "Hello";
echo $hello . ", world!";