Is PHP7 significantly different from PHP5, and can tutorials for PHP5 still be useful?

PHP7 introduced several new features and improvements over PHP5, such as improved performance, scalar type declarations, return type declarations, null coalescing operator, spaceship operator, and more. While many concepts from PHP5 are still relevant in PHP7, there are differences in syntax and functionality that may require updates to tutorials or code written for PHP5. 

<?php
// PHP7 code
function greet(string $name): string {
    return "Hello, $name!";
}

echo greet("John");
?>

Keywords

PHP7 PHP5 tutorials backward compatibility differences

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