http://php.net/manual/en/reserved.keywords.php
| __halt_compiler() | abstract | and | array() | as |
| break | callable (as of PHP 5.4) | case | catch | class |
| clone | const | continue | declare | default |
| die() | do | echo | else | elseif |
| empty() | enddeclare | endfor | endforeach | endif |
| endswitch | endwhile | eval() | exit() | extends |
| final | finally (as of PHP 5.5) | for | foreach | function |
| global | goto (as of PHP 5.3) | if | implements | include |
| include_once | instanceof | insteadof(as of PHP 5.4) | interface | isset() |
| list() | namespace(as of PHP 5.3) | new | or | |
| private | protected | public | require | require_once |
| return | static | switch | throw | trait (as of PHP 5.4) |
| try | unset() | use | var | while |
| xor | yield (as of PHP 5.5) |
| __CLASS__ | __DIR__(as of PHP 5.3) | __FILE__ | __FUNCTION__ | __LINE__ | __METHOD__ |
| __NAMESPACE__(as of PHP 5.3) | __TRAIT__(as of PHP 5.4) |