<?php $listOfIntegers = [1, 2, 3, 4]; $myObject = new stdClass(); $myObject->integers = $listOfIntegers; echo json_encode($myObject) . PHP_EOL; // Output of the code above will be: `{"integers":[1,2,3,4]}` // Now some refactoring has to be made since the requirement changed. The requirement now is that the integers list // must not contain odd values anymore. So `array_filter` to the rescue, right? $listOfEvenIntegers = array_filter([1, 2, 3, 4], static fn (int $integer): int => $integer % 2 === 0); $myObject = new stdClass(); $myObject->integers = $listOfEvenIntegers; echo json_encode($myObject) . PHP_EOL; // Output of the refactored code above now became: `{"integers":{"1":2,"3":4}}` // So what now happened is a huge problem for highly type-sensitive API clients since we changed a list to a hashmap // Same happens with hashmaps which suddenly become empty. $hashmap = [ 'foo' => 'bar', ]; $myObject = new stdClass(); $myObject->map = $hashmap; echo json_encode($myObject) . PHP_EOL; // Output of the code above will be: `{"map":{"foo":"bar"}}` // So now some properties are being added, some are being removed, the definition of your API says // "the object will contain additional properties because heck I do not want to declare every property" // "so to make it easier, every property has a string value" // can be easily done with something like this in JSONSchema: `{"type": "object", "additional_properties": {"type": "string"}}` // Now, some string value might become `null` due to whatever reason, lets say it was a bug and thus the happy path always returned a string // The most logical way here is, due to our lazyness, to use something like `array_filter` to get rid of all our non-string values $hashmap = [ 'foo' => null, ]; $myObject = new stdClass(); $myObject->map = array_filter($hashmap); echo json_encode($myObject) . PHP_EOL; // Output of the refactored code above now became: `{"map":[]}` // So in case that every array value is being wiped due to the filtering, we suddenly have a type-change from // a hashmap to a list. This is ofc also problematic since we do not want to have a list here but an empty object like // so: `{"map":{}}`
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