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