PHP symbol table, what to do with

PHP symbol table

There are some questions about the symbol table
1, so understanding right
(1) The symbol table is a key-value structure, just like a database. For each new variable, a record is added to the symbol table.
(2) When $a=1, add a piece of data to the symbol table, the key is a,value to the address of the memory, assuming 0x111222. When the $b= is $a, the value of B corresponds to 0x111222.
2, when $c = & $a, will be forced to separate. Some problems with obsessive-compulsive disorder come, who separates? Is 0x111222 this address is $b, or $a/$c?
3, about unset ($a), online information is said to be disconnected, how disconnected? Is it actually removing the $ A record from the symbol table?
------to solve the idea----------------------

$a = 12;

$b = $a;

$c = & $a;

echo $b. " _ ". $c; 12_12

$a = 15;

echo $b. " _ ". $c;//12_15

?>

& As a reference variable or function address, this & is similar to the C language pointer, $b = $a; just assign the value of variable A to the variable B, and when variable a changes, the variable B does not change
------to solve the idea----------------------
It feels like this:
$b = $a only assigns the value of A to B, and does not give the address to B;
$c =& $a is a reference assignment that separates the address of A to C, which means a is what C is.
unset ($a), disconnect, in fact, will be the address of a point to disconnect, such as you said 0x111222, just will be the point to disconnect the connection, but the value of this address still exists ....

Probably not very clear.
I hope I can help you.
------to solve the idea----------------------
1. Your understanding is correct
2. $c = & $a copy a $b $c, $a point to 0x111222
3.unset ($a) just remove $ A from symbol_table and put a $ A zval--recount if Recount==0 then GC

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