PHP被称为“二进制安全”的功能是什么？ 这些“非二进制安全”函数向哪些库移除字符串？ 为什么？

Question

I'm using Windows 10 Home Single Language Edition which is a 64-bit Operating System on my machine.

I've installed the most latest version of XAMPP which has installed PHP 7.2.7 on my machine.

I'm asking this question based on the excerpt taken from the PHP Manual :

The string in PHP is implemented as an array of bytes and an integer indicating the length of the buffer. It has no information about how those bytes translate to characters, leaving that task to the programmer. There are no limitations on the values the string can be composed of; in particular, bytes with value 0 (“NUL bytes”) are allowed anywhere in the string (however, a few functions, said in this manual not to be “binary safe”, may hand off the strings to libraries that ignore data after a NUL byte.)

I understand very well the difference between binary-safe and non-binary safe functions in PHP. I've following doubts in my mind. Please answer them in one-by-one fashion with appropriate explanation accompanied with suitable examples.

• Is the phenomenon of "non-binary safe" and "binary-safe" functions present in PHP only because the entire PHP parser has been written in C language?
• What are the differences between C and PHP in case of handling strings containing any value(including NUL byte)?
• I want the complete lists of functions in PHP which are "non-binary safe" and which are "binary-safe".
• Is the characteristic of "non-binary safe" and "binary-safe" applicable only to functions that manipulate over strings and not applicable to PHP functions that deal with other types in PHP?
• Why do the non-binary safe functions hand off the strings to libraries?
• Do the non-binary safe functions hand off the strings to libraries only when the string they are handling contains NUL byte?
• What are those libraries to which these "non-binary safe" functions hand off the strings?
• How these libraries handle the strings received from "non-binary safe" functions?
• Do the "non-binary safe" functions work like "binary safe" functions after handing off the strings that contain NUL byte to some library?

Answer 1

Like arkascha explained, the issue of "binary-safe" and "non-binary-safe" has nothing to do with the language.

Using a null byte (0x00) to indicate the end of the string is simpler (which is probably why C went with it), but the downside is you can't have a null byte anywhere in the string which is a big limitation if you have to be able to handle all kinds of data. Storing the length as a metadata part of a string is more complex, as shown by Pete, but it allows you to handle any kind of data.

Regarding which functions that are "binary-safe" or "non-binary-safe", just read the PHP Manual before using the functions. That's what I do. There is no need to construct a list because the PHP Manual already explains what you need to know about the functions, including if they are binary-safe or not.

Most of your post, I believe, is due to a misunderstanding of PHP Manual's explanation that you quoted, particularly this part:

however, a few functions, said in this manual not to be “binary safe”, may hand off the strings to libraries that ignore data after a NUL byte.

Let me try making it clearer by adding some of my own words:

however, a few functions, said in this manual not to be “binary safe”, are the functions that may hand off the strings to libraries that ignore data after a NUL byte.

So it really doesn't say "non-binary safe functions hand off the strings to libraries", this is a misinterpretation. What it means is "functions that may hand off the strings to libraries that ignore data after a NUL byte, are said in this manual as not binary-safe".

"Handing off to libraries" is just another way of saying "calling functions from other libraries". "Ignoring data after a NUL byte" is a behavior that is called not binary-safe.

Another way of putting it is:

A few functions in this manual are said not to be "binary safe" because they may call other functions that are also not "binary safe" (functions that ignore data after a NUL byte).

I hope this clears it up for you.