daily-email: add 2023-08-20

PHP types and assertions

src/content/daily-email/2023-08-20.md

@@ -0,0 +1,57 @@
+---
+title: >
+  PHP types and assertions
+pubDate: 2023-08-20
+permalink: >
+  archive/2023/08/20/php-types-and-assertions
+tags:
+  - php
+---
+
+Following yesterday's email about input validation, guard clauses and assertion libraries, these can be used to compliment PHP's native types and checking.
+
+For example:
+
+```php
+function createJourney(string $from, string $to, int $duration): void {
+  var_dump($from, $to, $duration);
+}
+```
+
+In this code, each parameter has a type, but there's no validation on the values.
+
+If I run this:
+
+```plain
+createJourney('', '', -10);
+```
+
+I would get this output:
+
+```plain
+string(0) ""
+string(0) ""
+int(-10)
+```
+
+This is probably not what you want.
+
+I expect `$to` and `$from` to be not empty and the duration to be greater than zero.
+
+## Here's the thing
+
+I can use an assertion library or throw my own Exceptions if the values pass the type checks but aren't what I need.
+
+For example:
+
+```php
+function createJourney(string $from, string $to, int $duration): void {
+  Assert::stringNotEmpty($from);
+  Assert::stringNotEmpty($to);
+  Assert::positiveInteger($duration);
+
+  var_dump($from, $to, $duration);
+}
+```
+
+Now, if an empty string or negative duration is passed - in my implementation or test code - an Exception will be thrown.