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)) { }
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23 May 2020 at 06:30 PM
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.
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24 May 2020 at 12:24 PM
Tim
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