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Using PHP isset to Easily Check the Value of Variables

Reading time 2 min
Published Aug 5, 2019
Updated Sep 30, 2019

Web Development Course:

When you’re coding in PHP, your code holds multiple variables more often than not. It’s not that hard to get lost among them either. To make PHP check if a variable exists, you can use PHP isset(). Its name is rather self-explanatory: by using isset in PHP, you check whether a particular variable in the script is set or not.

PHP isset: Main Tips

  • By using isset in PHP, you can check whether a particular variable is set.
  • It returns a boolean value, True meaning a variable is set.
  • Just as echo and print, isset in PHP is a language construct and not a function.
  • To unset a particular variable in PHP, use the unset() function.

How to Use and Write isset() Correctly

PHP isset() determines whether a particular variable is set:

Example
$x = 'SpaceDoggo';
var_dump(isset($x));

It returns a boolean value, which is only True if all three conditions below are satisfied:

  • The variable is declared (has a value assigned).
  • This value is not Null.
  • The variable hasn't been unset using the unset() function.

The syntax for making PHP check if a variable exists with isset() is simple:

Example
isset($x)

You can use PHP isset() to check one or multiple variables, thus saving time:

Example
isset($x, $y, $z)

Note: if you check more than one variable, PHP isset will only return True if all of them are set.

Checking Variables in PHP: isset vs empty

To check the value of a certain PHP variable, you can also use PHP empty(). However, you should understand how different it is to isset():

Example
$x = 'EarthKitten';

var_dump(isset($x));
var_dump(empty($x));

The purpose of isset() and empty() seem alike and they both return boolean values. However, as you can see in the example, they return opposite values:

  • isset() returns True for set variables.
  • empty() returns True for unset or empty ones.

Note: one more difference is that empty() can take expressions as arguments, while isset() cannot.

PHP isset: Summary

  • To check if a certain variable is set, you can use PHP isset().
  • It is not actually a function, but a language construct, similarly as echo and print.
  • If checked variable is set, it returns a boolean value of True.
  • Variables can be unset with an unset() function.