If I return nothing explicitly, what does a php function exactly return?
function foo() {}
What type is it?
What value is it?
How do I test for it exactly with === ?
Did this change from php4 to php5?
Is there a difference between function foo() {} and function foo() { return; }
(I am not asking how to test it like if (foo() !=0) ...)
nullnullif(foo() === null)You can try it out by doing:
$x = foo();
var_dump($x);
?string but it will give error like TypeError: Return value must be of type ?string, none returned. In such cases you need to explicitly return null. See: php.net/manual/en/migration71.new-features.php#122592Not returning a value from a PHP function has the same semantics as a function which returns null.
function foo() {}
$x=foo();
echo gettype($x)."\n";
echo isset($x)?"true\n":"false\n";
echo is_null($x)?"true\n":"false\n";
This will output
NULL
false
true
You get the same result if foo is replaced with
function foo() {return null;}
There has been no change in this behaviour from php4 to php5 to php7 (I just tested to be sure!)
return null; on : void but have to return null; on (for example) : ?string when no string is returned.I did find an oddity when specifying function return types. When you do, you must be explicit about returning something from your functions.
<?php
function errorNoReturnDeclared($a = 10) : ?string {
if($a == 10) {
echo 'Hello World!';
}
}
errorNoReturnDeclared(); //Fatal error
Error:
Uncaught TypeError: Return value of errorNoReturnDeclared() must be of the type string or null, none returned in
So if you decide to add some return type specifications on old functions make sure you think about that.
Return value must be of type ?string, none returned