PHP5中文手册·Class Constants -- 追寻梦想＞编程乐园＞PHP 编程

Class Constants

It is possible to define constant values on a per-class basis remaining the same and unchangeable. Constants differ from normal variables in that you don't use the $ symbol to declare or use them.

The value must be a constant expression, not (for example) a variable, a class member, result of a mathematical operation or a function call.

As of PHP 5.3.0, it's possible to reference the class using a variable. Keywords like self, parent or static are not allowed in dynamic class references.

Example#1 Defining and using a constant


<?php
class MyClass
{
    const constant = 'constant value';

    function showConstant() {
        echo  self::constant . "\n";
    }
}

echo MyClass::constant . "\n";

$classname = "MyClass";
echo $classname::constant . "\n";

$class = new MyClass();
$class->showConstant();

echo $class::constant."\n";
?>


	PHP5中文手册 Static Keyword Class Abstraction 类与对象（PHP 5） PHP Manual Class Constants It is possible to define constant values on a per-class basis remaining the same and unchangeable. Constants differ from normal variables in that you don't use the `$` symbol to declare or use them. The value must be a constant expression, not (for example) a variable, a class member, result of a mathematical operation or a function call. As of PHP 5.3.0, it's possible to reference the class using a variable. Keywords like self, parent or static are not allowed in dynamic class references. Example#1 Defining and using a constant `<?php class MyClass { const constant = 'constant value'; function showConstant() { echo self::constant . "\n"; } } echo MyClass::constant . "\n"; $classname = "MyClass"; echo $classname::constant . "\n"; $class = new MyClass(); $class->showConstant(); echo $class::constant."\n"; ?>` Static Keyword Class Abstraction 类与对象（PHP 5） PHP Manual