Difference between PHP if $variable, isset(), empty(), strlen()

What is the difference between PHP functions below ?

if ($variable) { }
if (isset($variable)) { }
if (!empty($variable)) { }
if (strlen($variable)) { }

posted on 23.05.2020 at 18:30

onefive

Hi,

The differences between those PHP functions are visible in specific cases. For example when variable is created, is NULL, is 0, is TRUE or FALSE etc.

In the condition if ($variable) { echo "OK"; } the output will be OK when $variable:

is not empty
is TRUE
is not FALSE
is not 0
is not NULL

In the condition if (isset($variable)) { echo "OK"; } the output will be OK when $variable:

is set and is different from NULL

In the condition if (!empty($variable)) { echo "OK"; } the output will be OK when $variable:

is not empty
is TRUE
is not FALSE
is not 0
is not NULL

In the condition if (strlen($variable)) { echo "OK"; } the output will be OK when $variable:

is not empty
is TRUE
is not FALSE
is not NULL

In relation to these functions, you can use is_null() to find out if variable is NULL.

posted on 24.05.2020 at 12:24

Tim