Useful terms and functions in PHP

self keyword in PHP
__DIR__ in PHP
$_ENV in PHP
PHP_SAPI in PHP
PHP_EOL in PHP
implode() in php
explode() in php
headers_sent() in php
header() in PHP
ini_get() in php
max_execution_time in php
ini_get() and ini_set() functions in PHP
fwrite() in PHP
STDERR in PHP
trigger_error() in PHP
spl_autoload_register() in PHP
spl_autoload_unregister() in PHP
call_user_func() in PHP
unset() in PHP
empty() in PHP
call_user_func_array() in PHP
array_merge() in PHP
throw in PHP
InvalidArgumentException class in PHP
apcu_fetch() in PHP
HHVM_VERSION in PHP
apcu_add() in PHP
strtr() in PHP
strrpos() in PHP
substr() in PHP
file_exists() in PHP
stream_resolve_include_path() in PHP
$GLOBALS in PHP
Closure class in php
Closure::bind in PHP