是否有必要在php中使用连接赋值运算符之前定义变量？

Question

I've tried and came to know that if i use

$a .="test";
$a .=" test2";

and echo out $a

echo $a

it returns

test test2

also for arrays

<?php 
$testarray['Title'] = "test";
$testarray['text'] = "text";
 print_r($testarray); 

 ?>

it gives the proper result without declaring $testarray=[];

Array ( [Title] => test [text] => text )

It does not even shows the warning or notice.. so i just want to know is it good practice to declare the variable before or both are ok.. also if it is related to any particular php version.. i am using php 7.1 will it show error in earlier version?

Answer 1

No, not necessary but it is good practice to declare/initialize your variables first.

Actually, if you follow any coding standards you would clearly avoid using the concatenation assignment operator; you get the PHP notice for a reason for doing so.

The second case is not necessarily bad. If an array variable is used in a closure and there is no ambiguity it's arguably fine. But if we talking about a large file, a class property, or another critical piece, you arguably still doing it wrong when you use (associative) arrays that way.

The general advice here is, follow the coding standards that the framework at hand puts forth. Most bigger frameworks have a coding guide (here is a nice overview), otherwise stick to PSR-2 and PSR-1 or some custom coding standard (e.g. this); the important thing is: be consistent.