PHP String Indexing 'error'

Question

Without wanting to sollicate the obvious Q&A, I'm wondering if anybody knows why the following happens.

I have a string variable $string with the value '1011100001111'

Testing for a '1' or '0' at a certain position:

$string[00] => '1'  // correct
$string[01] => '0'  // correct
$string[07] => '0'  // correct
$string[08] => '1'  // should be '0'
$string[ 8] => '0'  // correct

It took me a while to find the error when using prefix zeroes, and obviously I got rid of them, but why is index 08 different from 8? Note that up to 07 it does work!

If I remember correctly, when you use 08, it uses the hex value of that number, not the decimal value. So it's not looking where you think it is. — aynber
– aynber, Commented Feb 8, 2017 at 14:16
To use octal notation, precede the number with a 0 (zero). To use hexadecimal notation precede the number with 0x. To use binary notation precede the number with 0b. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Feb 8, 2017 at 14:18
@WiktorStribiżew Ah, octal, not hex. Thanks for clearing that up. :-D — aynber
– aynber, Commented Feb 8, 2017 at 14:19
PHP7 gives a Parse error: Invalid numeric literal in... i.e. 08 is an invalid octal number — RiggsFolly
– RiggsFolly, Commented Feb 8, 2017 at 14:29

Matt S · Accepted Answer · 2017-02-08 14:47:24Z

5

From the documentation regarding integers:

To use octal notation, precede the number with a 0 (zero)

So 08 is not the integer 8 and therefore not returning the index you expect. It's an invalid octal and resolves to 0.

edited Feb 8, 2017 at 14:47

answered Feb 8, 2017 at 14:20

Matt S

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2 Comments

RiggsFolly Over a year ago

But There is good news. In PHP7 it will generate a Parse Error

Han Timmers Over a year ago

Thanks for clearing that up. Makes me wonder what the result is if I use 008. I will try and find out.

aniri · Accepted Answer · 2017-02-08 14:24:08Z

0

If you precede the numbers with 0, they will be considered octal numbers. So from 00 to 07, they are equivalent to 0-7 decimal. But 08 does not exist in octal so it resolves to 0.

answered Feb 8, 2017 at 14:24

aniri

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