php "||" assignment logic compared to Javascript -

i testing heredoc , || functionality

function test() {     $obj = [(object)['col1'=>'val1'],             (object)['col2'=>'val2'],             (object)['col3'=>'val3']];     $output = ''; $mystring = <<<eot non empty string eot;      foreach($obj $prop)     {         foreach($prop $i)         {             $output .= <<<eot             <div style='background-color:lightblue'>              \$head  : {gettype($i)}              </div> eot;         }     }     $out =  $output || $mystring || 'couldn\'t find valuable';     echo $out; } test(); 

i output of

1

which represents boolean true. had output contents of $mystring @ 1 point putting logic in brackets eg

echo ($output || $mystring); 

and used output:

a non empty string

it stopped working straight after , not sure change broke it.

in javascript:

    function test()      {                var obj = [{'col1':'val1'},                  {'col2':'val2'},                  {'col3':'val3'}];          var output = '';          var mystring ="a non empty string";                for(var prop in obj)          {              for(var in prop)              {                  output +=                   "<div style='background-color:lightblue'>" +                      + " : " + typeof prop[i] +                      "</div>";              }          }          out =  output || mystring || 'couldn\'t find valuable';          document.write(out);          console.log("outputting \n\t" + out);      }      test();

it different php in terms of logic || during assignment works expected.

0 : string

0 : string

0 : string

for code above. if comment out inner loop so

for(var prop in obj) {     /*for(var in prop)     {         output +=          "<div style='background-color:lightblue'>" +         + " : " + typeof prop[i] +         "</div>";     }*/ } 

i contents of "mystring" is

a non empty string

and if change mystring empty string so

mystring = ""; //"a non empty string"; 

i

couldn't find valuable

how php's "||" during assignment work ? can explain it?

if assign conditional expression in php boolean (that is, strictly true or false), not work in javascript "truthy" value gets assigned, in php

$a = ""; $b = 42; $c = ($a || $b); // == true 

while in javascript

var = ""; var b = 42; var c = (a || b); // == 42 

and is, sadly, language design.

as @billyonecas reports, in comments docs: http://php.net/manual/en/language.operators.logical.php#77411

to obtain similar behaviour in php, must like:

$a = ""; $b = 42; $c = ($a ?: $b); // newer php version $c = ($a ? $a : $b); // older php version 

if need concatenate expression, use parethesis:

$c = ($a ? $a : ($b ? $b : "not found"));