An array contains a series of information. Retrieving a single piece of information involves iterating over a loop, such as foreach or calling the index directly using the array name and the index. For example,
In several places, I use information in the array to determine whether to load something else. For example, if the thread system is enabled then do something.
if ( $this->options['use_thread_system'] == true )
The challenge in the above code is first looking for the existence of the 'use_thread_system' index. If it doesn't exist then PHP returns a notice. The program now has a bug, as well as unexpected results.
A better way to write the conditional is to include the array_key_exists, which takes two parameters, the key and the array.
if ( array_key_exists( 'use_thread_system', $this->options ) && $this->options['use_thread_system'] == true )
This code stops the undefined index notice and makes sure the conditional is run only when the thread system is enabled.