Ensure files end with a single line break.

[PSR-2] The closing ?> tag MUST be omitted from files containing only PHP.
[PSR-2] A file must always end with an empty line feed.
Remove short PHP tags.

[PSR-1] PHP code must use the long <?php ?> tags or the short-echo
<?= ?> tags; it must not use the other tag variations.
Remove multiple empty lines.
Adjust spaces in function declaration to match standard.

[PSR-2] Spaces should be properly placed in a function declaration
Remove trailing spaces.

[PSR-2] Remove trailing whitespace at the end of lines.
Fix spacing around control structures.

A single space should be between: the closing brace and the control,
the control and the opening parentheses, the closing parentheses and
the opening brace.
Replace “else if” with “elseif”

[PSR-2] The keyword elseif should be used instead of else if so that
all control keywords looks like single words.
Ensure all return statements are preceded by a new line.
Ensure all properties and methods have visibility declarations.

[PSR-2] Visibility must be declared on all properties and methods;
abstract and final must be declared before the visibility; static must
be declared after the visibility.
Ensure include paths are (more) consistently formatted.
Convert tabs to spaces.