NULL vs unset()?

PHP
1

Recently I noticed that setting a variable to NULL causes it to evaluate as unset, tho no warning or errors are thrown if the variable is mentioned later in the script if the variable is used.

echo $myVAr;  // throws warning
echo isset($myVar) ? 'yes':'no'; //echoes 'no'
$myVAr.+=" more text"';  // throws warning
echo isset($myVar) ? 'yes':'no'; //echoes 'no'
$myVA =" some text";
echo isset($myVar) ? 'yes':'no'; //ouputs 'yes'
echo $myVAr;   // ouputs " some text";
$myVA = NULL;
echo $myVAr.' nothing!';   // ouputs ' nothing!';
echo isset($myVar) ? 'yes':'no'; //ouputs 'no'?!?

I what is the method the islet function uses to figure out that a variable is set?
I thought it checked to see if the variable was used in the namespace , regardless of value?
If you have a variable that holds the value of NULL, how could you set if it’s checked?

thanks all , in advance

2

Use is_null function or strict equality operator === to check if a variable contains NULL.

The docs for PHP isset function clearly state that when NULL is passed the function returns FALSE.

3

oops that’s what I get from typing on my phone.

My question was actually if you could check if a a variable IS set EVEN if it’s set to NULL.

note that checking for a NULL value on an unset variable will throw a warning, but checking to see if it’s UNSET first wont give you a definite answer as to whether it’s unset because it’s not set at all or or unset because it is equal to NULL.