The difference between const and define in PHP

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

if (... {     const FOO = ' BAR ';    // if (.....    ) {     define//

4, const uses a common constant name, define can use the expression as the name.

Const  FOO = ' BAR ' for ($i$i < + +$i)     {define$ I$i

5, const can only accept static scalar, and define can use any expression.

Const Bit_5 = 1 << 5;    //   define// 

6, const is always case sensitive, however define () can use the third parameter to define a case insensitive constant

Define true);  Www.2cto. com Echo //  echo//

Summarize:
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.

<?  class  animal {    const type= ' Person1 ';     function Call ()     {        echo self::type;    }} Define (' name ', ' Zhaoxingzhuang '); $person New animal (); Call ( $person); Echo ' <br/> '; Echo name;? >