number as variable name in php

Question

number as variable name not possible right? But this works

 ${4} = 444;
 echo ${4};

Question: How much is this justified using this syntax? and where is info about this in documentation? I not found.

Answer 1

The syntax is covered in Variable variables . No, you are not "justified" in using this syntax. You should absolutely never do this , there is no good reason for using a number as a variable name.

Answer 2

Variables between brackets are considered valid (variable variables), no matter the syntax.

${'sad asda sda'} = 444;
echo ${'sad asda sda'};
// still works.

Answer 3

this is also works

$_4 = 444;
echo $_4;  //output 444.

Answer 4

This is a perfectly ok json string:

$json_str = '{"1": "One", "02": "Two"}';

So if I were to decode it:

$json_object = json_decode($json_str);

the way to access the elements is:

$one = $json_object->{1};
$two = $json_object->{"02"};