Logical Operators and Precedence

Question

So I just did some random test and understand the fundamentals of Precedence and the || and or operators but I'm having trouble understanding why $f changes:

$f = 0 || 1;

if ($f === 1){
    echo "TRUE - $f";
}else{ 
   echo "FALSE - $f";
}
$f = 0 or 1;

if ($f === 0){
    echo "TRUE - $f";
}else{ 
   echo "FALSE - $f";
}

Thanks for some insight.

Answer 1

It's normal to evaluate always to True. The reason is that OR means if that one of the values is True it will take this one.

Update to your new question:

The answer is that "||" has a greater precedence than "or"

// The result of the expression (false || true) is assigned to $e
// Acts like: ($e = (false || true))
$e = false || true;

// The constant false is assigned to $f and then true is ignored
// Acts like: (($f = false) or true)
$f = false or true;

You can learn more at the PHP manual website here which I found this example

Answer 2

What you are doing is the same as :

if (($f = 0) or 1){ 
    // $f is being assigned the value 0, and the condition evaluates 0 or 1,
    // 1 being equivalent to true, the condition is always true.
    echo "TRUE - $f";
}else{
    echo "FALSE - $f";
}

and

if ($f = (0 || 1)){ // which gives $f = true which returns true
    echo "TRUE - $f";
}else{
    echo "FALSE - $f";
}

if you want to check if $f is equal to a value or another you would do

if ($f === 0 or $f === 1)

Be aware that in php, by default an int 1 will be evaluated to bool true unless you do a strict comparison === or !==

Answer 3

the problem is here: "if ($f = 0 or 1){" :

"=" means you give the variable $f the value 0

You should use :

• "==" : checks if the values are equal
• "===" : checks if the left variable is identical to the right variable (value, type, etc.)