Fatal error: Cannot use isset() on the result of an expression

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When coding with isset i am getting an fatal error.I have searched stackoverflow but results are not satisfactory.

I am getting

Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)

My codes are

if (!isset( $size || $color )) {
    $style = '';    
}else{
    $style = 'font-size : ' . $size . ';color:' . $color;   
}

As mentioned in the comments (and the error message), you cannot pass the result of an expression to isset.

You can use multiple isset calls, or reverse the logic of your if/else block and pass multiple parameters to isset, which i think is the cleanest solution:

//true if both are set
if(isset($size, $color)) {
    $style = 'font-size : ' . $size . ';color:' . $color;
}else{
    $style = '';
}

You can clean this up a little further by setting the default value first, thus avoiding the need for an else section:

$style = '';
if(isset($size, $color)) {
    $style = 'font-size : ' . $size . ';color:' . $color;
}

You could even use a ternary, though some people find them harder to read:

$style = isset($size, $color) ? 'font-size : ' . $size . ';color:' . $color : '';

PHP Fatal error: Cannot use isset() on the result of an expression , PHP Fatal error: Cannot use isset() on the result of an expression (you can use "​null !== expression" instead) #42. Closed. shajamansoor  Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) This is line 10. if (isset($_GET['page']=="logout")) {. Here's the "entire" part of that code: session_destroy(); echo '<script>document.location.href="shipper.php"</script>';} php.

you should use this way

if  (!isset( $size ) || !isset( $color ))  {

Fatal error: Cannot use isset() on the result of an , Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in E:\wamp64\www\web3_test\src\Utils.php on line 280 #  PHP Fatal error: Cannot use isset() on the result of an expression (you can use “null !== expression” instead) in /var/www/html/index.php on line 14

Your expression always return either true or false => In theory isset always return true so PHP not allow this Change

if (!isset( $size || $color )) {

To

if (!isset($size) || !isset($color)) {

Fatal error: Cannot use isset() on the result of an expression in , Fatal error: Cannot use isset() on the result of an expression in ViewsFieldFormatter.php on line 323. Closed (fixed). Project: Views field  Hi, I got this error: Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in C:\\xampp\\htdocs\\test\\rec

Fatal error: Cannot use isset() on the result of a function call , Fatal error: Cannot use isset() on the result of a function call. Closed (fixed). Project: Lingotek Translation. Version: 7.x-7.x-dev. Component:. Answers: As mentioned in comments (and the error message), you cannot pass the result of an expression to isset. You can use multiple isset calls, or reverse the logic of your if/else block and pass multiple parameters to isset, which i think is the cleanest solution: //true if both are set if (isset ($size, $color)) { $style = 'font-size : ' . $size . ';color:' . $color; }else { $style = ''; }

A Look At PHP's isset() - DEV, It does not accept an expression​​ While regular functions and other language constructs can accept the result of any expression, due to its unique nature, isset() can only accept a variable, array key or object property as an argument. Attempting to use it any other way will result in a fatal error. Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) in F:\xamppnew\htdocs\650032\admin\delete.php on line 6

Fatal Error: Cannot use isset() on the result of an expression , Hi,. I got this error: Fatal error: Cannot use isset() on the result of an expression (​you can use "null !== expression" instead) in  PHP Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead) #42 shajamansoor opened this issue Sep 18, 2017 · 9 comments Assignees

Comments
  • You're trying to do $size || $color and then see if that's set: use if (!isset( $size ) || !isset( $color )) {
  • Possible duplicate of Isset expression error or Compile Error: Cannot use isset() on the result of an expression or Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)
  • why donwvote without motivation .. the answer is correct