Upgrading to PHP 7

Chapter 5. Expectations and Assertions

PHP has had an assert() function since PHP 4; it gives you the ability to add sanity-checks to your code. assert() is intended for development use only, and it can be easily enabled and disabled using assert_options() or the assert.active INI setting.

To use assertions, you pass in either an expression or a string as the first argument. If you pass in a string, it is evaluated by the assert() function as code. If the expression result, or the result of evaluating the string evaluates to false, then a warning is raised.

Example 5-1. Using assertions

assert('$user instanceof \MyProject\User');
assert($user instanceof \MyProject\User);

Single versus double quotes

Ensure that you use single quotes; otherwise, variables will be interpolated.

In Example 5-1, we see the same assertion using a string and an expression. If either of these evaluates to false, then a warning is raised:

Warning: assert(): Assertion "$user instanceof \MyProject\User" failed in <file> on line <num>

Using string assertions

While eval() is typically frowned upon, if you pass a string into assert() and assertions are disabled, the string is not evaluated at all. Using strings is considered best practice.

Expectations

With PHP 7, assert() has been expanded by the Expectations RFC, allowing for so-called zero-cost assertions.

With this change, you not only disable assertions, but you can also remove all overhead entirely. With this setting, assertions are not compiled, ...