PHP Foreach Loop Efficiency

Using $class->getAttributes() outside of the foreach loop and using a temporary variable, or keeping it like you wrote should not change anything about performances : it will still be evaluated only once.

And here is an example that proves it :

function get_array() {
 echo 'function called !<br />';
 return array(
 'first' => 123,
 'second' => 456,
 'last' => 789, 
 );
}
foreach (get_array() as $key => $value) {
 echo "$key : $value<br />";
}

I am using a function and not a method of a class, to get a shorter example, but the principle would be the same with a class+method.

And calling this portion of code gives the following output :

function called !
first : 123
second : 456
last : 789

i.e. the get_array() function is only called once, at the beginning of the foreach loop.

foreach operates on a copy internally:

Note: Unless the array is referenced, foreach operates on a copy of the specified array and not the array itself. [...]

So it doesn’t make any difference in your case. $class->getAttributes() is only called once to retrieve the array.

I haven't tested, but I'd think that doing something like this:

$attributes = $class->getAttributes();
foreach($attributes as $attribute)
{
}

Is more readable, and you can get to the attributes after the foreach has conclude if you need to.

However, in a more direct response to your question, getAttributes() will only be called once in either case.

As others have said, the function in your example is only called once.

The case in which pre-evaluating can make a difference is for loops.

$str = 'abcdefghijklmnop';
//strlen will be called on every iteration
for($i = 0; $i < strlen($str); $i++);
//strlen will only be called once
$len = strlen($str);
for($i = 0; $i < $len; $i++);

• php
• arrays