How to check whether a variable is set or not in PHP

Topic: PHP / MySQL« Prev|Next »

Answer: Use the PHP isset() function

You can use the PHP isset() function to test whether a variable is set or not. The isset() will return FALSE if testing a variable that has been set to NULL.

  • <?php
  • $var1 = '';
  • if(isset($var1)){
  •     echo 'This line is printed, because the $var1 is set.';
  • }
  • echo "<br>";
  •  
  • $var2 = 'Hello World!';
  • if(isset($var2)){
  •     echo 'This line is printed, because the $var2 is set.';
  • }
  • echo "<br>";
  •  
  • // Unset the variable
  • unset($var2);
  •  
  • if(isset($var2)){
  •     echo 'This line is printed, because the $var2 is set.';
  • } else{
  •     echo 'This line is printed, because the $var2 is not set.';
  • }
  • echo "<br>";
  •  
  • $var3 = NULL;
  • if(isset($var3)){
  •     echo 'This line is printed, because the $var3 is set.';
  • } else{
  •     echo 'This line is printed, because the $var3 is not set.';
  • }
  • ?>

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