What is the realtime use of PHP pack and unpack function?

Question

I saw some file generation codes which uses the pack function.

echo pack("ssssss", 0x809, 0x8, 0x0, 0x10, 0x0, 0x0);

What this is doing exactly?

s signed short (always 16 bit, machine byte order)

I dont know why i am not able to understand this in realtime. Am not asking a theoretical answer

When i execute the php , file got generated with some stange characters which is not identified by ms excel.

I just want to know the use of pack(), where to use and how to use?

When you need it, you'll know. Try to explain to a tribe of primitive, isolated humans why anyone "needs" air travel. — Lightness Races in Orbit, Apr 19 '11 at 16:48
@Tomalak Geret'kal your name says that you are from primitive tribe:-) — zod, Apr 19 '11 at 17:04
It's writing raw binary. Examine the output with the commandline tool `od -x`, or a GUI "hex editor" to get a better idea of what the output of this line is. In this case, this is apparently a BIFF8 header. BIFF format details are available here: http://sc.openoffice.org/excelfileformat.pdf — Frank Farmer, Apr 19 '11 at 17:04
possible duplicate of [Can someone explain me the pack() function in PHP?](http://stackoverflow.com/questions/987854/can-someone-explain-me-the-pack-function-in-php) — Lightness Races in Orbit, Apr 19 '11 at 17:07
Real-time - real life ... whatever, as long as you keep it real, bro! — aefxx, Aug 07 '16 at 12:13

Maxime Pacary · Accepted Answer · 2017-04-12T07:22:14.450

3

pack is generally used to generate raw binary data. For example, I saw it used to generate zip files before native functions/classes were available in PHP for that.

edited Apr 12 '17 at 07:22

answered Apr 19 '11 at 17:07

Maxime Pacary

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To '-1' voter: any comment so I can improve my answer? – Maxime Pacary Jan 08 '14 at 14:56

score 1 · Answer 2 · edited May 23 '17 at 12:17

When would you need to use mysql_connect? When connecting to a MySQL database. Why? To connect to a MySQL database.

When you'll realize that you just got this bad-ass lines of Hex numbers and you need to convert them to ASCII, or when you want to generate a .exe from user input (don't), or when you want to write a Little-Endian encoder, or a bunch of other stuff, you'll use pack.

If you just want to understand what pack does, there's already a question for it. But WHEN to use it? Well, when you want to pack data into a binary string.

What is the realtime use of PHP pack and unpack function?

2 Answers2

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