为什么我收到此通知当我通过array_key_exist进行检查时

Question

Please tell me why I receive this message While I use array_key_exists?

 <td width="91">'.(array_key_exists ( 1 , $famstand )) ? $famstand[1] : "" .'</td>

Undefined offset: 1

Answer 1

The problem is operator precedence. . has higher precedence than :?, so this is being parsed as:

('<td width="91">'.(array_key_exists ( 1 , $famstand ))) ? $famstand[1] : "" .'</td>'

The concanetation returns a non-empty string, which is truthy, even though the key doesn't exist, so it's trying to access the array element.

Add parentheses around the tertiary:

<td width="91">'.(array_key_exists(1 , $famstand) ? $famstand[1] : "") .'</td>