问题
While writing a recent application I accidentally started filling an array before I had declared it.
error_reporting ( E_ALL);
$array['value'] = 'Test string';
I use E_ALL error reporting and an error was not thrown. Is this correct? And if so, are there any issues with declaring array values whilst never declaring the actual array? Perhaps it just doesn't follow good programming standards.
回答1:
While writing a recent application I accidentally started filling an array before I had declared it.
PHP is a weakly typed language. Your statement:
$array['value'] = 'Test string';
is an implicit declaration (through assignment) of an associative array. So, a notice will not be generated.
However, if you were to write:
echo $array['value'];
before an assigment, then you'll receive an Undefined variable notice.
回答2:
No, you don't have to
And yes, it is a good habit to declare the array to increase code redability
回答3:
To expand on that, no you do not "have" to, but it can be beneficial to.
Also if you have E_NOTICES turned OFF then you will not see errors from an non uninitialized variable. On production you should turn it off, but on development you should turn it ON. It'll allow you to find problems that you might not see.
来源：https://stackoverflow.com/questions/3704557/does-a-php-array-need-to-be-declared-before-use