empty() vs. ! $var

[MickeyKay]

Would love to hear your thoughts on conditional testing for empty/defined variables in PHP. What are your thoughts on best practices, and suggested use cases for the following (and any I'm missing) conditional tests for a specific variable:

• empty()
• ! $var
• is_null()
• isset()

Thanks!

[bueltge]

Conditional testing is always usable in the context of the goal. Best practices for me is, use the fastest and exact test for the requirement.

• empty — Determine whether a variable is empty
• ! $var — is the same as $var == FALSE. Also, one should take into account that type conversion takes place when using == operator.
• is_null — Finds whether a variable is NULL
• isset — Determine if a variable is set and is not NULL

Maybe the table below give you an overview. It give not the one point solution.

Value of variable ($var)	isset($var)	empty($var)	is_null($var)
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 $var; (a variable declared, but without a value)		bool(true)	bool(true)
NULL byte ("\ 0")	bool(true)

Maybe we lost the tables in markdown, below a screenshot: