How to check if a variable is undefined in PHP
In this tutorial, we are going to see how to check if a variable is undefined in PHP. You can use PHP’s isset() function to check if a variable is set or not. isset() will return FALSE if you are testing a variable that has been set to NULL.
See also : How to check if a variable is null in PHP
See also : How to check if a variable is empty in PHP
How to check if a variable is undefined in PHP
<?php
$foo = 'lorem ipsum';
if(isset($foo)){
echo 'foo is defined' . '<br />';
}else{
echo "foo is undefined" . '<br />';
}
if(isset($bar)){
echo 'bar is defined' . '<br />';
}else{
echo "bar is undefined" . '<br />';
}
?>
Output:
foo is defined bar is undefined
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