Interpreting what the log tells you.
THE TYPES
- Parse error: a syntax mistake. The file will not run at all. Names the file and line.
- Fatal error: something the code cannot continue past, such as calling a function that does not exist.
- Warning: something wrong that did not stop execution.
- Notice and Deprecated: informational, but deprecations predict breakage on the next PHP version.
READING ONE
The message names the problem, the file and the line. Start there.
A stack trace, where present, shows how execution reached that point. Read from the bottom up to understand the path.
COMMON CAUSES
Calling a function removed in a newer PHP version A missing file after an incomplete upload A missing PHP extension Memory or execution time exhausted A type error after a PHP version change
CHECKING SYNTAX WITHOUT RUNNING
php -l against the file reports parse errors without executing it. Useful before deploying an edit.
AFTER A PHP VERSION CHANGE
Deprecation notices become fatal errors in later versions. Read them before upgrading rather than after.
