If $ a = 5, $ b = 'a', what is the value of $$ b?

Question

Explain this question to me:

Q: If the variable $ a is 5 and the variable $ b is equal to the character a, then what is the value of $$ b?

A: 5, reference to an existing variable.

Answer 1

This is a variable variable . PHP will look for a variable with the name stored in the string $b . Therefore, if $b == 'a' , then $$b == $a .

This is very similar to pointers to C, except that they use variable name strings instead of memory addresses to point to each other. And you can play as many times as you want:

 $a = 5; foreach (range('b', 'z') as $L) { $$L = chr(ord($L) - 1); } echo $$$$$$$$$$$$$$$$$$$$$$$$$$z; 

Output:

 5 

Answer 2

-95 is the answer, as if u will be echo $b u will be output as " a " and if u echo $a u will exit, but as " 5 "

therefore, in this sense, when u $(echo $b) , which matches $(a) , so u will get it as " 5-100 ", which is equal to " -95 "

Answer 3

  $$b - 100 = $a - 100 // substituting $b=a = 5 - 100 = -95 

Answer 4

Below is a good reference to PHP variables

http://php.net/manual/en/language.variables.variable.php

Answer 5

I don't know if '?' mistaken in the statement of '$$ b? - 100 ', but I don’t think it will compile.

But:

 $a = 5 $b = 'a'; $c = $$b - 100; 

$ c will be equal to -95 because $$ b is a variable reference variable and provided that $ a = 5 allows $ a (5) - 100 or -95.

Answer 6

the answer is -95

 $a - 100