Good day, I have three arrays A, B and C. Anyone of them might not have the 'id' key set which will give the Notice "Undefined index: id". I just wanted to know what the correct approach to this problem would be; without making the code overly complicated to read by introducing a number of "if isset" statements. if ($arrayA['id'] == $arrayB['id'] || $arrayC['id'] == $arrayB['id']) { } I have notices switched off, but I want to know the right way to do this. There's probably a number of different right ways to solve this, how would you do it? Best Regards, Nicholas