&& and 'and' are the same in php?

Question

I tried the following code and got && and and are different.

<?php

$keyWord =  2 and 3>4;

$symbol  =  2 &&  3>4;

echo $keyWord===$symbol ? 'equal' : 'not-equal';

output: not-equal

why?

and && are same in the case of operation but different in case of precedence — Arun Killu, Feb 21 '13 at 06:11

score 9 · Accepted Answer · answered Feb 21 '13 at 05:13

9

They do not have the same precedence. Fully parenthesised, your code is:

($keyWord = 2) and (3>4); // $keyWord = 2
$symbol = (2 && (3>4)); // $symbol = false

2 and false are clearly not the same, hence 'not-equal'.

answered Feb 21 '13 at 05:13

`$symbol = (2 && (3>4));` is this correct ?? I guess it should be `$symbol = (2 && 3)>4);` – Prasanth Bendra Feb 21 '13 at 05:26
@PrasanthBendra Erm... why? – Niet the Dark Absol Feb 21 '13 at 05:26
`&&` has more precedence than `>` – Prasanth Bendra Feb 21 '13 at 05:27
`($keyWord = 2)` - isn't that an assignment? – Hanky Panky Feb 21 '13 at 05:32
@PrasanthBendra Erm... no it doesn't! – Niet the Dark Absol Feb 21 '13 at 05:54
@HankyPankyㇱ: Absolutely. What's wrong with that? – Niet the Dark Absol Feb 21 '13 at 05:54
@Kolink : Why is that ? operator precedence says so please check the link : http://php.net/manual/en/language.operators.precedence.php – Prasanth Bendra Feb 21 '13 at 05:56
@Kolink Pardon, I must admit I didn't read the question and thought this was asked related to comparison. +1 and sorry. – Hanky Panky Feb 21 '13 at 05:56
@PrasanthBendra The table clearly shows that ` – Niet the Dark Absol Feb 21 '13 at 06:07
ohhhh... I am sorry I got confused with assignment operators :) +1 – Prasanth Bendra Feb 21 '13 at 06:10

score 3 · Answer 2 · answered Feb 21 '13 at 05:15

Well, altering the code slightly to:

<?php
$keyWord =  2 and 3>4;

$symbol  =  2 &&  3>4;

var_dump($keyWord);
var_dump($symbol);
?>

produces an output of:

int(2) bool(false)

As Kolink points out above, this is due to operator precedence.

Prasanth Bendra · Answer 3 · 2013-02-21T06:09:26.607

Here is the precedence of logical operators (part of the table)

left    &&  logical
left    ||  logical
left    ? :     ternary
right   = += -= *= /= .= %= &= |= ^= <<= >>= =>     assignment
left    and

In your case :

case 1:

$keyWord =  2 and 3>4;

($keyWord =  2) and (3>4);

Here $keyWord = 2

case 2:

$symbol  =  2 &&  3>4;

$symbol  =  (2 && (3>4));

Here $symbol = false

Solution : $keyWord = (2 and (3>4)); and $symbol = 2 && (3>4); Use brackets

3 Answers3