1. Const is used for class member variable definition, once defined and cannot change its value. Define defines global constants that can be accessed everywhere.
2. Define cannot be defined in a class and const can.
3. Const cannot define constants in conditional statements
Copy CodeThe code is as follows:
if (...) {
Const FOO = ' BAR '; Invalid
}
But
if (...) {
Define (' FOO ', ' BAR '); Valid
}
4, const uses a common constant name, define can use the expression as the name.
Copy CodeThe code is as follows:
Const FOO = ' BAR ';
for ($i = 0; $i < + + + $i) {
Define (' Bit_ '. $i, 1 << $i);
}
5, const can only accept static scalar, and define can use any expression.
Copy CodeThe code is as follows:
Const BIT_5 = 1 << 5; Invalid
But
Define (' Bit_5 ', 1 << 5); Valid
6, const is always case sensitive, however define () can use the third parameter to define a case insensitive constant
Copy CodeThe code is as follows:
Define (' FOO ', ' BAR ', true);
Echo FOO; BAR
echo foo; BAR
Summary:
The use of const is simple and easy to read, it is itself a language structure, and define is a method, with a const definition at compile time much faster than define.
http://www.bkjia.com/PHPjc/327648.html www.bkjia.com true http://www.bkjia.com/PHPjc/327648.html techarticle 1. Const is used for class member variable definition, once defined and cannot change its value. Define defines global constants that can be accessed everywhere. 2. Define cannot be defined in a class and const can. ...
