PHP underlying analysis about forced splitting

Learning requires knowing what it is and why it is. The underlying knowledge of PHP is this kind of knowledge.

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Today we will talk about the knowledge about forced splitting. Simply put, forced splitting is "before the reference variable is actively assigned a value, the If a variable is assigned a value, forced splitting will occur."

It's a bit convoluted, let's take a look at the code analysis.

Look at the following code:

If you are slightly familiar with PHP: & reference symbols, you should be able to see that the output is gzchen, 8:30 in the evening, gzchen .

So let’s take a look at the underlying running process of the above code.

As we all know, a variable is a structure, which looks like this:

Comments are written on each line. This file is in zend.h in PHP Source code Zend directory.

When the code runs to line: 3[$name = '8:30 in the evening'], the structure in the memory looks like this:

When the code runs to line: 4[name], the structure becomes like this:

##Run to line: 5[

Misplaced &<span style="max-width:90%"></span>name] and line: [$nameCopy = 'gzchen'], like this:

Here, here, this is it A forced split occurred.

When is_ref__gc[reference attribute] is from 0->1, if refcont_gc>1, then forced splitting will occur. The pseudo code is:

#This is forced splitting. Variables that have been assigned by value are referenced and assigned again. The variable assigned by value will be split into a structure, in this case $myName.

This principle is basically not used in actual development, but forced splitting is usually tested together with

Copy while writing (cow) during interviews.

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