Which is easier as far as code maintainability and readability goes?

if_elseif_else.php

<?php

if($http_code >= 200 && $http_code < 300) {
	if($body == "foo") {
		// do something
	} else if($body == "bar") {
		// get drunk
	} else {
		// do something else
	}
	
	if($body != "bar") {
		// don't get drunk
	}
} else if($http_code == 404) {
	// not found?
} else if($http_code > 500) {
	// throw an exception?
} else {
	// handle default
}

switch_true.php

<?php

switch(true) {
	case $http_code >= 200 && $http_code < 300:
		if($body == "foo") {
			// do something
		} else if($body == "bar") {
			// go drinking
			break;
		} else {
			// do something else
		}
		// don't get drunk
		break;
	case $http_code == 404:
		// not found?
		break;
	case $http_code > 500:
		// throw an exception?
		break;
	default:
		// handle default
		break;
}

I would say the if-elseif-else is better. The switch statement is a bit of a misuse. If the HTTP code wasn't in certain ranges, then the switch would be better:

switch ($http_code) {
case 200:
...
case 300:
...
case 404:
...
case 500:
...
default:
...
}

The example was just using http code as it's a good example of ranges and conditionals.

Also, in dynamic languages, it's not a "misuse" and is something intentionally supported, especially in PHP/Ruby/Javascript.

I just mean that the switch is wasting an entire block level with "switch (true)", which is semantically useless. Personally, I only use switch for equality testing on a single expression.

The switch basically boils down to the if-elseif-else anyway, with a superfluous boolean:

if (true == ($http_code >= 200 && $http_code < 300)) {
...
} else if (true == ($http_code == 400)) {
...
} etc...

Then the answer becomes obvious that the first method was the best option.

You're right that it's a valid statement, but it's an unusual use of switch, which by virtue is less readable and maintainable.