isset(), empty() and is_null() functions; and the differences in responses.
| Value of Variable | isset() |
empty() |
is_null() |
|---|---|---|---|
| "" (an empty string) | bool(true) | bool(true) | |
| " " (space) | bool(true) | ||
| FALSE | bool(true) | bool(true) | |
| TRUE | bool(true) | ||
| array() (an empty array) | bool(true) | bool(true) | |
| NULL | bool(true) | bool(true) | |
| "0" (0 as a string) | bool(true) | bool(true) | |
| 0 (0 as an integer) | bool(true) | bool(true) | |
| 0.0 (0 as a float) | bool(true) | bool(true) | |
| var ; (a variable declared, but without a value) | bool(true) | bool(true) | |
| NULL byte ("") | bool(true) |
This page has been created as I kept losing where I found this on the internet. It covers certain PHP functions that have interesting functionality.
It's originally from https://www.virendrachandak.com/techtalk/php-isset-vs-empty-vs-is_null/ so thanks to them for that page! Super useful.