How reference notation (&) in PHP is used in the code explanation

PHP refers to a variable or function, object, and so on before the & symbol, in PHP refers to the meaning: different names to access the same variable content.

There is a difference between the pointers in the C language. The pointer inside the C language stores a reference to the address variable where the contents of the variable are stored in memory.
PHP references allow you to use two variables to point to the same content

$a = "ABC"; $b =& $a; echo $a;//output here: ABC echo $b;//output here: ABC $b = "EFG"; echo $a;//Here the value of $ A becomes EFG so the output EFG echo $b;//Output EFG here

Invocation of a function's address
Address call I'm not going to say much. Directly below the code

Function test (& $a) {$a = $a +100;} $b = 1; echo $b;//Output 1 Test ($b);   Here $b passed to the function is actually the memory address of the $b variable content, by changing the value of $ A in the function can change the value of the $b echo "<br>"; echo $b;//Output 101

It is important to note that here Test (1), the words will be wrong, reason to think
A reference to the function returns
Look at the code first

function &test () {static $b =0;//declares a static variable $b = $b +1; echo $b; return $b;} $a =test ();//This statement outputs $b value 1 $a = 5; $a =test ();//This statement outputs a value of $b of 2 $a =&test ();//This statement outputs a value of $b of 3 $a = 5; $a =test ();//This statement outputs a value of $b of 6

Explained below:
in this way $a=test (); The resulting is not a function of the reference to return, which is not the same as the normal function call the reason: this is the PHP provisions
PHP provisions through $a=&test ();
As to what is a reference return (the PHP manual says that reference return is used when you want to use a function to find out which variable the reference should be bound to.) I didn't read this shit for a long while.
using the example above to explain is
$a =test () call the function, just assign the value of the function to $ A, and $ A does not affect $b
in the function and call the function by $a=&test (). , his role is to refer to the memory address of the $b variable in the return $b to the same place as the memory address of the $ A variable
that produces the equivalent effect ($a =&b;) So changing the value of $ A also changes the value of $b so that it executes the
$a =&test ();
$a = 5; After the
, the value of the $b becomes 5.