What is & operator in php

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Reference - What does this symbol mean in PHP?

I was searching for a password generator tutorial, which I found one but somethings got me a little confused...

if ($strength & 2) {
$vowels .= "AEIOU";
}

What exactly is this operator? I know && equals "and" but just one &?

Was really annoying that half of my question got removed. – David Lawrence Dec 19 '11 at 01:53 — David Lawrence, Dec 19 '11 at 01:53

score 2 · Answer 1 · answered Dec 19 '11 at 01:43

2

That is called a bitwise operator. Learn more.

answered Dec 19 '11 at 01:43

Alex R.

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score 0 · Answer 2 · answered Dec 19 '11 at 01:43

0

It's the bitwise and.

answered Dec 19 '11 at 01:43

Zach Johnson

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score 0 · Accepted Answer · answered Dec 19 '11 at 01:45

0

As in most programming languages, & is the bitwise and operator. x & 2 tests whether the second (least significant) bit of x is set (2 is 10 in binary).

answered Dec 19 '11 at 01:45

Jan Pöschko

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Yes, except in VB.Net (and earlier VB's if I remember correctly), in which case it's the string concatenation operator. – Kibbee Dec 19 '11 at 01:46
So how in this way is $strength being tested? Cause its testing 1, 2, 4, and 8.. What do the 1 2 4 and 8 mean? – David Lawrence Dec 19 '11 at 01:48
Which you wouldnt know that cause some dude removed half my damn question cause its "possibly" a duplicate.. – David Lawrence Dec 19 '11 at 01:49
@David they are powers of two, which are 0001, 0010, 0100, and 1000 in binary, respectively. – Zach Johnson Dec 19 '11 at 01:50
@Zach Thanks bud.. Still dont understand it but ill just echo or print_r every step of the function till i do.. – David Lawrence Dec 19 '11 at 01:52
@David: from my cursory glance at the code that was edited out, it looks like the person who wrote that code is using $strength as a bitwise flag variable. – Zach Johnson Dec 19 '11 at 01:54
@Zach yea the code that was there wouldve helped quite a few people answer the follow up questions i had. Was really annoying that it was removed. Thanks again – David Lawrence Dec 19 '11 at 01:56
Testing against 1, 2, 4, and 8 means asking whether the first, second, third, and fourth bit of `$strength` are set. – Jan Pöschko Dec 19 '11 at 01:58
OHHHHHHHHHHHHHHHHHHHHHHHH Ok so 8 would mean that hte 4th bit is set, and 4 would be third and so on! OK! I get it now. Thanks! Btw do bits go higher than 4? Like if i did 16 wouldnt that mean that the 8th bit would be set? – David Lawrence Dec 19 '11 at 02:05
`x & 16` would test for the fifth bit (`16 = 2 ^ 4 = 10000` in binary). Of course, higher bits can be tested accordingly. Usually, integers have a size of 32 bit (signed). – Jan Pöschko Dec 19 '11 at 02:15

score 0 · Answer 4 · answered Dec 19 '11 at 01:50

& is the bitwise AND operator. It sets bits that are in both numbers that are tested.

Example: 6 & 4

6 ->     1 1 0
4 ->     1 0 0

6 & 4 -> 1 0 0 -> 4
6 & 4 = 4

Example: 13 & 10

13 ->     1 1 0 1
10 ->     1 0 1 0

13 & 9 -> 1 0 0 0 -> 8
13 & 9 = 8

What is & operator in php

4 Answers4