Check if a variable is undefined in PHP

Question

Consider this JavaScript statement:

isTouch = document.createTouch !== undefined

I would like to know if we have a similar statement in PHP, not being isset(), but literally checking for an undefined value. Something like:

$isTouch != ""

Is there something similar as the above in PHP?

Answer 1

You can use -

$isTouch = isset($variable);

It will return true if the $variable is defined. If the variable is not defined it will return false.

Note: It returns TRUE if the variable exists and has a value other than NULL, FALSE otherwise.

If you want to check for false, 0, etc., you can then use empty() -

$isTouch = empty($variable);

empty() works for -

• "" (an empty string)
• 0 (0 as an integer)
• 0.0 (0 as a float)
• "0" (0 as a string)
• NULL
• FALSE
• array() (an empty array)
• $var; (a variable declared, but without a value)