Logical Operators, || or OR?

php operators logical-operators or-operator

161,697

Solution 1

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;

Solution 2

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();

Solution 3

The difference between respectively || and OR and && and AND is operator precedence :

`$bool = FALSE || TRUE;`

interpreted as ($bool = (FALSE || TRUE))
value of $bool is TRUE

`$bool = FALSE OR TRUE;`

interpreted as (($bool = FALSE) OR TRUE)
value of $bool is FALSE

`$bool = TRUE && FALSE;`

interpreted as ($bool = (TRUE && FALSE))
value of $bool is FALSE

`$bool = TRUE AND FALSE;`

interpreted as (($bool = TRUE) AND FALSE)
value of $bool is TRUE

Solution 4

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>

Solution 5

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

View more solutions

161,697

Author by

ItsPronounced

Constantly learning web application development. Self taught ASP.NET and php since 2003.

Updated on December 28, 2020

Comments

ItsPronounced over 3 years

I remember reading a while back in regards to logical operators that in the case of OR, using || was better than or (or vice versa).

I just had to use this in my project when it came back to me, but I can't remember which operator was recommended or if it was even true.

Which is better and why?
giannis christofakis over 10 years

die() function will be called if doSomething() will return false or null? What if doSomething() returns true or nothing?
Matthew Ratzloff over 10 years

doSomething() is evaluated as a boolean. If it returns a value PHP considers truthy (true, a non-empty string, etc.), it will not call die().
Matt Kieran over 9 years

and $e = true || $x = 'foo' will not define $x because of short-circuiting, not because of higher precedence.
bzeaman over 9 years

This is not 'The Best Answer !!'. Please scroll back up and take the most up voted answer for a good explanation. With the ||, B will not be called. Both operators do exactly the same, except that the precedence is differs.
Jens A. Koch almost 8 years

"you should always use OR which is faster" Hmm, i wonder if this is true... so let's check that: 3v4l.org/5QSAA/vld#tabs 3v4l.org/PdjJP/vld#tabs The number of opcodes is the same. So it doesn't matter performance wise.
TextGeek over 6 years

It is also worth noting that these always return a boolean value, unlike many other languages where they return the last value checked. So in PHP (27 || 0) returns true, not 27.
WayFarer about 6 years

it's incorrect answer, the second example works exactly as first one
Zdeněk about 6 years

@WayFarer well, it's not correct (there is an issue) but you're wrong too (|| and OR is not the same) - see my edit
WayFarer about 6 years

right, operators || and 'or' have different priority, so, your second example works as: (($second = returnEmpty()) or []); So, the answer to original question would be || is better, always use it, until you really understand why do you want to use 'or'
bishop almost 6 years

$positions = $this->positions() ?? []; is likely what you want.
jinyong lee over 5 years

@TextGeek, "these"? 27 or 0 returns 27 for me.
TextGeek over 5 years

@Jānis Elmeris -- you are correct, I should have referred only to the "||" case.
jinyong lee over 5 years

@TextGeek, actually, you are right that or returns boolean as well. Just its precedence is so low that it sometimes looks like it does something else. :) print 27 or 0 would print 27 because or happens after print 27. BTW, echo is not fooled – echo 27 or 0 would output 1.
Peter Mortensen over 4 years

The link is broken.