Check if a variable exists

you're probably looking for the isset function

There are some kind of validations that you can do. Check this link from stack overflow with great examples :D

http://stackoverflow.com/questions/418066/best-way-to-test-for-a-variables-existence-in-php-isset-is-clearly-broken

@freekmurze isset won't check to see if there is a variable set give a string you pass to it, rather you need to pass it an actual variable

>>> isset('video');
PHP Parse error: Syntax error, unexpected T_CONSTANT_ENCAPSED_STRING on line 1
>>> $video = 'test';
=> "test"
>>> isset($video);
=> true
>>> isset($video1);
=> false

I need something like

<input type="text" name="title" value="<?= oldInputOrExistingValue('title', isset($video) ? $video : null) =>">

function oldInputOrExistingValue($field, $model) {
    return old($field, isset($model) ? $model->{$field} : null);
}

but where I pass the $model as a string in the view and not check again to see if I have the $video variable