variant_add

"Adds" two variant values together and returns the result (PHP 5)
mixed variant_add ( mixed left, mixed right )

Adds left to right using the following rules (taken from the MSDN library), which correspond to those of Visual Basic:

表 25. Variant Addition Rules

IfThen
Both expressions are of the string typeConcatenation
One expression is a string type and the other a characterAddition
One expression is numeric and the other is a stringAddition
Both expressions are numericAddition
Either expression is NULLNULL is returned
Both expressions are emptyInteger subtype is returned

See also variant_sub().

注意:

对于所有的变量算法函数,此函数的参数可以要么是 PHP 自身的类型(整型,字符串,浮点型,布尔型或者 NULL),要么是一个 COM,VARIANT 或 DOTNET 类的实例。PHP 自身类型将被转换为变量,使用与 VARIANT 类的构造函数中相同的规则。COM 和 DOTNET 对象将具有其默认属性的值,取得并作为变量值使用。

变量算法函数是 COM 库中与其名称接近的函数的封装。此类函数的更多信息请参考 MSDN 库。PHP 函数命名有少许不同,例如 PHP 中的 variant_add() 对应于 MSDN 文档中的 VarAdd()。