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100% true? Wow, this must be a first!

Say you have a variable:

PHP Code:

$var 


If you don't assign any value to it, the variable has not been instantiated yet. Therefore, it contains no value at all - in other words, it's null.

However, if you use:

PHP Code:

$var = ""; 


A value is being passed into the variable. Even though it's got a length of 0, it's still a string value - just a blank one. Therefore, the variable is now not null, as it contains a value (albeit a blank one).

Finally, if we pass a space to the variable:

PHP Code:

$var = " "; 


Here, the value passed has a length of 1 - in programming, a space is considered as just another ASCII character, just like a letter or number. Therefore, this variable is also not null, as it holds a normal value - the only difference is, the value isn't visible to humans, as it's used to fill a gap.