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There are five logical operator symbols: tilde, dot, wedge, horseshoe, and triple bar. Tilde is the symbol for negation. The word “not” and the phrase “it is not the case that” are used to deny the statement that follows them (we refer to their use as “negation”).
The logical-AND operator ( && ) has higher precedence than the logical-OR operator ( || ), so q && r is grouped as an operand. Since the logical operators guarantee evaluation of operands from left to right, q && r is evaluated before s-- .
There is no "better" but the more common one is ||. They have different precedence and || would work like one would expect normally.
See also: Logical operators (the following example is taken from there):
// 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)
$f = false or true;
They are used for different purposes and in fact have different operator precedences. The && and || operators are intended for Boolean conditions, whereas and and or are intended for control flow.
For example, the following is a Boolean condition:
if ($foo == $bar && $baz != $quxx) {
This differs from control flow:
doSomething() or die();
The difference between respectively || and OR and && and AND is operator precedence :
$bool = FALSE || TRUE;($bool = (FALSE || TRUE))
$bool is TRUE
$bool = FALSE OR TRUE;(($bool = FALSE) OR TRUE)
$bool is FALSE
$bool = TRUE && FALSE;($bool = (TRUE && FALSE))
$bool is FALSE
$bool = TRUE AND FALSE;(($bool = TRUE) AND FALSE)
$bool is TRUE
Source: http://wallstreetdeveloper.com/php-logical-operators/
Here is sample code for working with logical operators:
<html>
<head>
<title>Logical</title>
</head>
<body>
<?php
$a = 10;
$b = 20;
if ($a>$b)
{
echo " A is Greater";
}
elseif ($a<$b)
{
echo " A is lesser";
}
else
{
echo "A and B are equal";
}
?>
<?php
$c = 30;
$d = 40;
//if (($a<$c) AND ($b<$d))
if (($a<$c) && ($b<$d))
{
echo "A and B are larger";
}
if (isset($d))
$d = 100;
echo $d;
unset($d);
?>
<?php
$var1 = 2;
switch($var1)
{
case 1: echo "var1 is 1";
break;
case 2: echo "var1 is 2";
break;
case 3: echo "var1 is 3";
break;
default: echo "var1 is unknown";
}
?>
</body>
</html>
I know it's an old topic but still. I've just met the problem in the code I am debugging at work and maybe somebody may have similar issue...
Let's say the code looks like this:
$positions = $this->positions() || [];
You would expect (as you are used to from e.g. javascript) that when $this->positions() returns false or null, $positions is empty array. But it isn't. The value is TRUE or FALSE depends on what $this->positions() returns.
If you need to get value of $this->positions() or empty array, you have to use:
$positions = $this->positions() or [];
EDIT:
The above example doesn't work as intended but the truth is that || and or is not the same... Try this:
<?php
function returnEmpty()
{
//return "string";
//return [1];
return null;
}
$first = returnEmpty() || [];
$second = returnEmpty() or [];
$third = returnEmpty() ?: [];
var_dump($first);
var_dump($second);
var_dump($third);
echo "\n";
This is the result:
bool(false)
NULL
array(0) {
}
So, actually the third option ?: is the correct solution when you want to set returned value or empty array.
$positions = $this->positions() ?: [];
Tested with PHP 7.2.1
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