问题描述
I have this if statement that tests for the 2 conditions below. The second one is a function goodToGo() so I want to call it unless the first condition is already true
$value = 2239;
if ($value < 2000 && goodToGo($value)){
//do stuff
}
function goodToGo($value){
$ret = //some processing of the value
return $ret;
}
My question is about the 2 if conditions $value < 2000 && goodToGo($value). Do they both get evaluated or does the second one only get evaluated when the first one is true?
In other words, are the following 2 blocks the same?
if($value < 2000 && goodToGo($value)) {
//stuff to do
}
if($value < 2000) {
if (goodToGo($value)){
//stuff to do
}
}
No--the second condition won't always be executed (which makes your examples equivalent).
PHP's &&, ||, and, and or operators are implemented as "short-circuit" operators. As soon as a condition is found that forces the result for the overall conditional, evaluation of subsequent conditions stops.
From http://www.php.net/manual/en/language.operators.logical.php
// --------------------
// foo() will never get called as those operators are short-circuit
$a = (false && foo());
$b = (true || foo());
$c = (false and foo());
$d = (true or foo());
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