An error is a type of mistake. We can say an error is a condition of having incorrect or false knowledge or an error is defined as an unexpected, invalid program state from which it is impossible to recover.
Error can also be defined as "a deviation from accuracy or correctness". A "mistake" is an error caused by a fault: the fault being misjudgment, carelessness, or forgetfulness. An error message with filename, line number and a message describing the error is sent to the browser.
Types of error
Basically there are four types of errors in PHP, which are as follows: