How are foreach executed in PHP?

Question

foreach(func() as $item)...

The above will only call func() once,but why?What's happening exactly?

Answer 1

There's no need to call the function more than once - it should return an array that can be iterated over.

Answer 2

foreach accepts an array. You are essentially calling func() once yourself, and passing the resulting array to the foreach construct, which can loop over it.

Answer 3

foreach is not a control structure with a condition that is tested before or after each iteration like while, for or do … while. Instead it takes an array, makes an copy of it internally and iterates that.

The array can either be passed via a variable (most used variant):

foreach ($arr as $val) { /* … */ }

Or with another expression that returns an array when evaluated:

foreach (array('foo','bar') as $val) { /* … */ }

function f() { return array('foo','bar'); }
foreach (f() as $val) { /* … */ }