Set the type of variable
var to type.
Possibles values of
type are:
"boolean" (or, since PHP 4.2.0, "bool")
"integer" (or, since PHP 4.2.0, "int")
"float" (only possible since PHP 4.2.0, for older
versions use the deprecated variant "double")
"string"
"array"
"object"
"null" (since PHP 4.2.0)
成功回傳TRUE失敗回傳FALSE。
See also gettype(),
type-casting and type-juggling.