settype()

(PHP 4, PHP 5, PHP 7)

设置变量的类型

说明

将变量$var的类型设置成$type。

参数

要转换的变量。

$type的可能值为：

• “boolean”（或为“bool”，从 PHP 4.2.0 起）
• “integer”（或为“int”，从 PHP 4.2.0 起）
• “float”（只在 PHP 4.2.0 之后可以使用，对于旧版本中使用的“double”现已停用）
• "string"
• "array"
• "object"
• “null”（从 PHP 4.2.0 起）

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

Example #1settype()示例

注释

Maximum value for "int"isPHP_INT_MAX.

参见

• gettype() 获取变量的类型
• 类型转换
• 类型戏法

Note that you can't use this to convert a string 'true' or 'false' to a boolean variable true or false as a string 'false' is a boolean true. The empty string would be false instead... 

Just a quick note, as this caught me out very briefly:
settype() returns bool, not the typecasted variable - so:
$blah = settype($blah, "int"); // is wrong, changes $blah to 0 or 1
settype($blah, "int"); // is correct
Hope this helps someone else who makes a mistake.. ;)

Using settype is not the best way to convert a string into an integer, since it will strip the string wherever the first non-numeric character begins. The function intval($string) does the same thing.
If you're looking for a security check, or to strip non-numeric characters (such as cleaning up phone numbers or ZIP codes), try this instead: 

you must note that this function will not set the type permanently! the next time you set the value of that variable php will change its type as well.

To matt:
This function accepts a paremeter, which does not imply you using hardcoded stuff, instead you can let the user choose! \o/
As a part of a framework or something.
Plus, you can probably call this with call_user_func

Please note: 
When using settype to convert indexed arrays to objects, the properties of the typed object will be integers:
A brief example:
$a = ['1', '2'];
settype($a, 'object');
var_dump($a);
// output
object(stdClass)#1 (2) {
 ["0"]=>
 string(1) "1"
 ["1"]=>
 string(1) "2"
}

$foo = "1";
settype($foo, "bool");
var_dump($foo); // Outputs: bool(true)
$bar = "0";
settype($bar, "bool");
var_dump($bar); // Outputs: bool(false)

any digit except 0 or -0 are considered true in boolean, and any string except '0' or '' are also considered true.

The var_dumps both return the following:

The gettype echo will show the value as an integer.
So it seems that settype($val,'int') makes the conversion, 
but the function return value remains a string. 
Since settype returns a boolean, using 
 
is not a option.
I resolved my array value conversion using this instead:

Thanks to the posting here:
http://usrportage.de/archives/
808-Convert-an-array-of-strings-into-an-array-of-integers.html
Perhaps this will save someone else spinning wheels a bit. 
Also thanks to robin at barafranca dot com for 
pointing out the boolean return value of settype.

/**
  * @return bool
  * @param array[byreference] $values
  * @desc Convert an array or any value to Escalar Object [not tested in large scale]
  */
  function setobject(&$values) {
    $values = (object) $values;
    foreach ($values as $tkey => $val) {
      if (is_array($val)) {
        setobject($val);
        $values->$tkey = $val;
      }
    }
    return (bool) $values;
  }

note that settype() will initialize an undefined variable. Therefore, if you want to preserve type and value, you should wrap the settype() call in a call to isset().

prints "|0|", NOT "||".
To get the latter, use: 

settype() has some really strange, potentially buggy behavior.
As noted by Michael Benedict, using settype() on a variable will initialize that variable. What is stranger is that using settype() on an uninitialized variable that you are treating as an array or object will also initialize the variable. So:

This works for a chain of any length: $foo->bar['baz']->etc
Next we look at what happens if $foo is already set.

In and of itself, this wouldn't be problematic. It might even make sense. But in all other cases where $foo is defined, even if (boolean) $foo === false, it will throw an error unless $foo->bar is valid (i.e. $foo is an object already). 

If you attempt to convert the special $this variable from an instance method (only in classes) :
* PHP will silently return TRUE and leave $this unchanged if the type was 'bool', 'array', 'object' or 'NULL'
* PHP will generate an E_NOTICE if the type was 'int', 'float' or 'double', and $this will not be casted
* PHP will throw a catchable fatal error when the type is 'string' and the class does not define the __toString() method
Unless the new variable type passed as the second argument is invalid, settype() will return TRUE. In all cases the object will remain unchanged.

Here is the result :
Type         Succeed?       Converted
bool         1          Foo Object
(
)
Notice: Object of class Foo could not be converted to int in C:\php\examples\oop-settype-this.php on line 9
int         1          Foo Object
(
)
Notice: Object of class Foo could not be converted to float in C:\php\examples\oop-settype-this.php on line 10
float        1          Foo Object
(
)
array        1          Foo Object
(
)
object        1          Foo Object
(
)
Warning: settype(): Invalid type in C:\php\examples\oop-settype-this.php on line 14
unknowntype                Foo Object
(
)
NULL         1          Foo Object
(
)
Catchable fatal error: Object of class Foo could not be converted to string in C:\php\examples\oop-settype-this.php on line 15
If the class Foo implements __toString() :

So the first code snippet will not generate an E_RECOVERABLE_ERROR, but instead print the same string as for the other types, and not look at the one returned by the __toString() method.
Hope this helps ! :)

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