How can the use of single quotes vs. double quotes impact PHP code performance and readability?

Using single quotes instead of double quotes in PHP can improve performance because PHP does not have to evaluate the content within single quotes for variables or special characters. However, using double quotes can make the code more readable, especially when dealing with complex strings that contain variables or special characters. It is generally recommended to use single quotes for simple strings without variables and double quotes for strings that require evaluation.

// Using single quotes for improved performance
echo 'Hello, World!';

// Using double quotes for readability
$name = 'Alice';
echo "Hello, $name!";