php - How to assign first non false variable from a group of them -

i tried way without effect:

$a = false; $b = false; $c = 'sometext'; $result = $a or $b or $c or exit('error: variables false'); 

and $result should set $c, gives value of bool(false) instead.

there's couple of things going on here:

firstly, in php result of boolean operation boolean.

secondly, , more subtly, "english" boolean operators (or , and) have low precedence - lower assignment operator, =.

therefore in expression $result actual value of $a (regardless of $a's value), since assignment applied before boolean operator.

// has same effect: $result = $a or $b or $c;  // this: $result = $a; $a or $b or $c; // has no effect 

this confusing, , not want.

to boolean result of whether of $a, $b, $c truthy (ie true, or castable true) can either use parentheses force precedence, or use "c-style" operators (|| , &&) have higher precedence:

// these have same effect:  $result = ($a or $b or $c); $result = $a || $b || $c;  if ($a or $b or $c)   $result = true; else   $result = false;  if ($a || $b || $c)   $result = true; else   $result = false; 

if you're unsure operator precedence it's best use parentheses - tend make code more readable, since order of evaluation made more obvious.

it's better not rely on implicit type conversions (especially casting non-numeric strings), since tends make unclear code.

edit:

to answer actual question, approach (though don't recommend in case, since you're interested in first non-false value) use array_filter without callback - return array of all values in input array truthy, keys preserved.

eg:

$a = false; $b = false; $c = 'sometext'; $result = array_filter(array($a, $b, $c));  var_dump($result); 

outputs:

array(1) {   [2]=>   string(8) "sometext" }