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Introduction to PHP Functions
Returning NULL
What about functions without return
statements? Any function without a return
returns a special value NULL
. NULL
is a special data type that stands for the absence of a value.
function returnNothing() { echo "I'm running! I'm running!\n"; } $result = returnNothing(); // Prints: I'm running! I'm running! echo $result; // Nothing is printed
Let’s walk through the code above:
- We defined a function
returnNothing()
— thereturnNothing()
function prints"I'm running! I'm running!\n"
but has no return statement. - We defined the variable
$result
and assigned it the value returned when we invokereturnNothing()
. - Since we invoked the function,
I'm running! I'm running!
is printed. - Because the function does not have a return statement, the value assigned to
$result
isNULL
- Finally, we print the
$result
variable, but, since its value isNULL
, nothing is printed.
Let’s play around with NULL
!
Instructions
1.
Write a function createVacuum()
which returns nothing.
2.
NULL
can be really quirky. You don’t need to worry about the details now. But, just for fun, uncomment the line we provided at the bottom of the code. Predict what it will output to the terminal. When you have a guess, run the code to see.