According to the PSR2 coding standard:
The keyword elseif SHOULD be used instead of else if so that all control keywords look like single words.
Noncompliant Code Example
if ($expr1) {
...
} else if ($expr2) {
...
} else {...}
Compliant Solution
if ($expr1) {
...
} elseif ($expr2) {
...
} else {...}
