PHP有短路评估吗？

Question

Given the following code:

if (is_valid($string) && up_to_length($string) && file_exists($file)) 
{
......
}

If is_valid($string) returns false, does the php interpreter still check later conditions, like up_to_length($string)?
If so, then why does it do extra work when it doesn't have to?

Answer 1

Yes, the PHP interpreter is "lazy", meaning it will do the minimum number of comparisons possible to evaluate conditions.

If you want to verify that, try this:

function saySomething()
{
    echo 'hi!';
    return true;
}
 
if (false && saySomething())
{
    echo 'statement evaluated to true';
}