Does a PHP array need to be declared before use?

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 开发者_JS百科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.

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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.

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No, you don't have to

And yes, it is a good habit to declare the array to increase code redability

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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.