1. What is language structure
Language structure: It is the keyword of the PHP language and part of the language grammar; it cannot be defined by the user or added to a language extension or library; it may or may not have variables and return values.
2. The reason why language structures execute quickly
Functions must first be decomposed into language structures by the PHP parser (Zend engine). Therefore, functions have one more layer of parser analysis than language structures, and the speed is relatively slow
3.What are the language structures in php
echo()
print()
die()
isset()
unset()
include(), note that include_once() is a function
require(), note that require_once() is a function
array()
list()
empty()