What each means.
FATAL ERROR
Execution stops. The page does not render.
Usually a missing function, a missing file, or a syntax error.
PARSE ERROR
A syntax error in the code. Nothing runs at all.
Usually a missing bracket or semicolon, frequently from a recent edit.
WARNING
Something went wrong and execution continued.
Worth investigating. Frequently a missing file or a failed operation.
NOTICE AND DEPRECATED
Minor issues and code that will break in future versions.
Not urgent and worth addressing before a version upgrade.
THE MEMORY ERROR
Allowed memory exhausted. Either raise the limit or find what is consuming it.
THE TIMEOUT
Maximum execution time exceeded. The operation took too long.
WHAT TO ACT ON
Fatal and parse errors, immediately.
Warnings, when convenient.
Notices, before upgrading PHP.
WHAT THE LINE NUMBER MEANS
Where the error surfaced, not always where the cause is.
