함수 is defined()

1 Bash

a=hello
if [ -n "$a" ]; then
	echo "Yes"
else
	echo "No"
fi
# Yes
if [ -n "$b" ]; then
	echo "Yes"
else
	echo "No"
fi
# No

2 PHP

$a = 1;
var_dump( isset($a) );
# bool(true)
var_dump( isset($b) );
# bool(false)

3 같이 보기

• 함수 unset