Undefined offset

Description

This notice is emitted when an offset (string or integer) is being used before being defined. In a word, the elemenent at this offset is not created yet, so PHP creates it on the fly, as NULL, then uses it.

Example

<?php

echo [1,2,3][4];

?>

Solutions

• Test the existence of the offset before usage.

• Gives the offset a default value before usage.

In more recent PHP versions, this error message is now Undefined array key.