PHP variable "default value" - php

Question

I want to get a value from the session, but use a default if it is not defined. And ofcourse I want to circumvent the PHP notice.
You can write a function that does this
function get(&$var, $default){
if(isset($var)) return $var;
return $default;
}
echo get($foo, "bar\n");
$foobar = "foobar";
echo get($foobar, "ERROR");
Example in action
Is there a way to do this without defining this function in every file?

Answer 1

You can define it in one script and then require_once that script in your other scripts
You could also just use the ternary operator:
$myVar = isset($var)?$var:$default;

Answer 2

From PHP 7, you can now use the null coalescing operator :
$var ?? $default
that does exactly like your function

Answer 3

Use this concise alternative:
isset($myVar) || $myvar=$default;
The || operator is short circuit, it will not evaluate second operant if the first one be evaluated true.

Answer 4

The Null coalescing operator has been added to PHP version 7.0, what it does is replaces
$username = isset($_GET['user']) ? $_GET['user'] : 'nobody';
with a shorter version:
$username = $_GET['user'] ?? 'nobody';
What the line above does, is check if $_GET['user'] is set, and not null, then it will assign that to the $username variable, if $_GET['user'] is not set (and thus null) it will default to the 'nobody' string so $username is nobody.
Your code should look like:
echo $foo ?? "bar\n";
$foobar = "foobar";
echo $foobar ?? "ERROR";

Answer 5

Use less code to do what you need.
You don't need to specify the variable again using the _?_:_ format.
echo $var?:"default";
Is the same as
echo $var?$var:"default";
Now as far as an empty check, you could use # to mute notices, I'm not sure of the technical ramifications, but you're already doing your own checking while using this format:
echo #$non_existing_var?:"default";
Some examples:
<?php
$nope = null;
$yup = "hello";
echo ($nope?:$yup) . "\n" ;
echo ($yup?:$nope) . "\n" ;
$items = [ 'one', 'two', false, 'three', 'four', null ];
foreach($items as $item):
echo($item?:"default shown (".var_export($item,true).")")."\n";
endforeach;
echo(#$non_existing?:"default for non-existant variable!");
?>
Output:
$ php variabledefault.php
hello
hello
one
two
default shown (false)
three
four
default shown (NULL)
default for non-existant variable!%

Answer 6

You could use my tiny library ValueResolver in this case, for example:
$myVar = ValueResolver::resolve($var, $default);
and don't forget to use namespace use LapaLabs\ValueResolver\Resolver\ValueResolver;
There are also ability to typecasting, for example if your variable's value should be integer, so use this:
$id = ValueResolver::toInteger('6 apples', 1); // returns 6
$id = ValueResolver::toInteger('There are no apples', 1); // returns 1 (used default value)
Check the docs for more examples