PHP: Undefined index even after checking IsSet

arrays, indexing, php, undefined-index

Solution

The ternary expression:

isset($extensionData['Calories']) ? $extensionData['Calories'] : ''

is OK when used stand-alone like this:

echo isset($extensionData['Calories']) ? $extensionData['Calories'] : '';

$tmp_var = isset($extensionData['Calories']) ? $extensionData['Calories'] : '';

return isset($extensionData['Calories']) ? $extensionData['Calories'] : '';

because it is equivalent to the expected:

if(isset($extensionData['Calories']))
{
    // use $extensionData['Calories']
}
else
{
    // use empty string ''
}

but, when used in string concatenation then you need parenthesis in order to confine the scope of the comparison so that the leading string is not part of the comparison

echo '<p>' . (isset($extensionData['Calories']) ? $extensionData['Calories'] : '') . '</p>';

Doing (wrong way):

echo '<p>' . isset($extensionData['Calories']) ? $extensionData['Calories'] : '' . '</p>';

is equivalent to

if('<p>' . isset($extensionData['Calories'])) // The leading string is used in the comparison and the result of isset() (boolean) is appended to the string so 100% of the time this example will be true because of how loose comparisons work
{
    echo $extensionData['Calories']; // Produces Undefined index error
}
else
{
    echo '' . '</p>';
}

In conclusion:

When in doubt, add parenthesis.

When not in doubt, add parenthesis anyways because the code will be more legible when you have to re-visit it in 6 months. Most text editors have parenthesis and bracket match highlighting so adding parenthesis is a very beneficial way to declare and later see the operation's intended behavior.

See Operator Precedence if you come across someone's cryptic code and need help figuring out what on Earth they were thinking and/or failed to consider.

Problem

I have read the other questions, none have answered nor helped me. Here is my issue, I have an object/array which contains a property which is also an object/array. I have successfully accessed similar properties before via: ``` $variable[propertyObject][property] ``` However, I have been receiving the error Notice: Undefined index lately. Here is the code: ``` $extensionData = $data['Data']; echo '<p>' . isset($extensionData['Calories']) ? $extensionData['Calories'] : '' . '</p>'; ``` However, that still throws the same error. Even when I check: `isset($extensionData['Calories'])`, it always resolves to 1/True which means the property should exist, so how can the index be undefined? And when I do a var_dump or print_r of `$extensionData`, this is what I get: ``` Array ( [Calories] => 295 [WebDesktopImage] => https://clutch-asset-management.s3.amazonaws.com/elevation-burger/IMG_0760-Edit.jpg [WebMobileImage] => https://clutch-asset-management.s3.amazonaws.com/elevation-burger/IMG_0760-Edit.jpg [WebDescription] => BLT image ) ```

Original source