"Adds" two variant values together and returns the result

说明

variant_add ( mixed $left , mixed $right ) : mixed

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

**Variant Addition Rules**
If	Then
Both expressions are of the string type	Concatenation
One expression is a string type and the other a character	Addition
One expression is numeric and the other is a string	Addition
Both expressions are numeric	Addition
Either expression is NULL	NULL is returned
Both expressions are empty	Integer subtype is returned

参数

left: The left operand.
right: The right operand.

Note:
对于所有变量运算函数，本函数的参数可以是 PHP 内置的类型（整数，字符串，浮点数，布尔型或者 NULL），或者是一个 COM，VARIANT 或者 DOTNET 类的实例。PHP 内置类型将会使用和构造VARIANT类相同的规则转换成变量。COM 和 DOTNET 对象的值将会取其默认属性并被当成变量值使用。

变量运算函数是同名函数在 COM 库中的外包；有关此类函数的更多信息参见 MSDN 库。PHP 函数命名有少许区别，例如 PHP 中的 variant_add() 对应于 MSDN 文档中的 VarAdd()。

返回值

Returns the result.

参见

variant_sub() - Subtracts the value of the right variant from the left variant value