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PHP settype 设置变量的类型

settype

(PHP 4, PHP 5)

settype设置变量的类型

描述

bool settype ( mixed $var , string $type )

将变量 var 的类型设置成 type

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)

成功时返回 TRUE, 或者在失败时返回 FALSE.

Example #1 settype() 示例

<?php
$foo 
"5bar"// string
$bar true;   // boolean

settype($foo"integer"); // $foo 现在是 5   (integer)
settype($bar"string");  // $bar 现在是 "1" (string)
?>

参见 gettype()类型转换类型戏法


PHP settype note #1

Use intval instead of settype for integers. Much more reliable.

PHP settype note #2

With reply to Chris Sullins and Michael Benedict, I don't find this behavior strange:

<?php
 
echo var_dump( (int)'' );                    // int(0)

 
echo var_dump( (float)array('a'=>'b') );    // float(1)
?>

This is due to the fact that an uninitialized variable is null, which converts to a 0. As does boolean false or an empty string or array.
When a value is not empty, such as my above array, it is converted to a 1 (integer/float) or true (boolean).
When changing between arrays and objects, it of course made sense to keep the fields intact (array key/values and object properties/values).

Cheers,
Chris.

PHP settype note #3

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:

<?php
settype
($foo->bar,"integer"); // stdClass Object ( [test] => 0 )
?>

This works for a chain of any length: $foo->bar['baz']->etc

Next we look at what happens if $foo is already set.

<?php
$foo
= false;
settype($foo->bar,"integer"); // stdClass Object ( [test] => 0 )
?>

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).

<?php
$foo
= true;
settype($foo->bar,"integer"); // Notice: Trying to get property of non-object
?>

PHP settype note #4

You can change variable type also in another way instead of using function settype().

<?PHP
$a
= '125'; //$a is string
var_dump($a);

$a *= 1; //this convert $a to integer
var_dump($a);

$a *= 1.0; //$a is converted to float
var_dump($a);

$a .= ''; //now $a is string again
var_dump($a);

$a = NULL; //and finally $a is null
var_dump($a);
?>

With this you can easily change variable type to string, float or integer (but you can't change float to integer).

Positive side effect of this is that it is about 50% faster than using settype() function. This is because simple expression is executed more quickly than function.

PHP settype note #5

In trying to convert an array of strings to an array of ints,
I attempted to use settype with array_walk.

<?php
//$numArray is generated by another process
$numArray = array('13','14','33');

var_dump($numArray);

//my conversion function
function str_to_int($val){
 
//remember: settype($x, 'int') returns boolean (1=success, 0=failure)
  //--> so return $x to return new value
   
settype($val,'int');
    echo
"<br />gettype = ".gettype($val)."<br />";
    return
$val;
}

array_walk($numArray,'str_to_int');

var_dump($numArray);
?>

The var_dumps both return the following:
<?php
array(3) { [0]=> string(2) "13" [1]=> string(2) "14" [2]=> string(2) "33" }
?>

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
<?php $val = settype($val, 'int'); ?>
is not a option.

I resolved my array value conversion using this instead:
<?php
$numArray
=
     
array_map(create_function('$value', 'return (int)$value;'),$numArray);
?>
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.

PHP settype note #6

Yes, just look for the ampersand (&) in the function signature. Here you see:

bool settype  ( mixed &$var  , string $type  )

There is an & before the first parameter ($var). This means the variable is passed in by reference. So the function is working with the original variable and not a copied local version. You will see this in other php functions such as asort();

References Explained: http://us3.php.net/manual/en/language.references.php

PHP settype note #7

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.. ;)

PHP settype note #8

Possible value is "unicode" starting PHP6.

PHP settype note #9

In response to the guy who was having troubles with leading zeros and wrote the convertToInt function.

I benchmarked it and it is faster to just use base_convert than ltrim & friends.

base_convert also has a lower "first time call" cost than ltrim (this could be related to server settings).
It's about 2/3 that of ltrim.

If you only use this type of conversion once per script then it's far more beneficial to use base_convert.

The average values listed are ignoring the first time call costs.
<?php

$t
= '0100';

// avg: 0.0000025 (0.0000036 wrapped as a function)
$x = base_convert($t, 10, 10);

// avg: 0.0000028 (0.0000039 wrapped as a function)
$x = 0+ltrim($t,'0');
?>

PHP settype note #10

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

PHP settype note #11

using (int) insted of the settype function works out much better for me. I have always used it. I personally don't see where settype would ever come in handy.

PHP settype note #12

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().

<?php
settype
($foo, "integer");
echo(
"|$foo|");
?>

prints "|0|", NOT "||".

To get the latter, use:
<?php
if(isset($foo)) settype($foo, "integer");
echo(
"|$foo|");
?>

PHP settype note #13

James Reiher (IL) writes:
23-Feb-2005 06:50

$agentnum = "007";
$agentnum = settype($agentnum, "int");
echo $agentnum; // will show up as 1 instead of 7!

James, the return value of settype function is boolean, 1 if succsess.
Correct code: $success=settype($agentnum, "int");
The $agentnum is now 7 (not 007 or not 1)!

PHP settype note #14

In response to the comment by Neoja regarding validating every variable in the URL using settype -- that is wrong.

All value passed in the URL are strings, even if they are numbers. (Remember, they are passed in the header, which is a specially formatted string).

PHP settype note #15

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.

PHP settype note #16

I needed to pull a zerofilled integer out of a MySQL table and increment it by a certain amount.  Unfortunately, PHP treated this integer as if it were a string when I tried to add an amount to it.  For instance:

<?php
$a
= '0100';
$b = $a + 1;
print
$b;
// This would print 64 instead of 101.
?>

To fix this I created a simple function:

<?php
function convertToInt($string) {
   
$y = ltrim($string, '0');
   
$z = 0 + $y;
    return
$z;
}
// Now I can add any integer to my converted integer
$a = '0100';
$b = 2 + convertToInt($a);
print
$b;
// This prints 102
?>

PHP settype note #17

Instead of settype you could use:
<?php

$int
=593// $int is a integer

$int.="";   // $int is now a string

PHP settype note #18

I had a problem with PHP destroying the value of my integer with leading zeros as follows:

$agentnum = "007";
$agentnum = settype($agentnum, "int");
echo $agentnum; // will show up as 1 instead of 7!

Oddly enough, this works fine, (at least for PHP 4.3):
$agentnumber = "007";
$agentnumber += 0; // convert $number to numeric type
echo $agentnumber; // will now show up as 7!

If you do this for gods sake leave a comment on the line because its definitely not by-the-book coding. Another commentor here has used regular expressions to weed out the leading zeros, so I know its not the only solution.

I also tried the equivelant of:
$agentnum = "007";
$agentnum = (int)$agentnumber;
echo $agentnum;

But the result is a nonsense number, probably by using the concatenation of the ASCII codes as the integer.

PHP settype note #19

/**
    * @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;
    }

PHP settype note #20

in PHP3 converting a string to any number results in the value becoming 0.  To check if a string represents a number try this:
<PRE>
$test = "0001";
$testcp = $test;
settype($testcp,"double");

if (strval($testcp) === $test) {
   echo("$test is a number");
} else {
   echo ("$test is not a number");
}
</PRE>

PHP settype note #21

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:

<?
     $number=ereg_replace("[^0-9]","",$number);
?>

PHP settype note #22

Usually it won't be necessary to use this function, but some times you need to be sure the variables are of some kind. For example, if you send a number to a database query from a variable passed by GET or POST, you may get sure it's a number by doing SetType ($var, 'integer'); so you can avoid security holes if it isn't a number and you don't need to addslashes() it, or for example, if you need to be sure that a number won't have any decimals after rounding it, you may do the same and as it will be an integer, it won't contain decimals.

(ed: change to reflect deleted of other notes)

PHP settype note #23

To: neoja@hotmail.com

I believe in this case testing the $id using is_numeric() would be the better solution.

E.g something like this:

<?php
 
if (is_numeric($id)) {
 
$db->query($sql);
 }
?>

Roman Schechtel

PHP settype note #24

It is always good to validate all the variables that are given in the url and would cause an error if they are of wrong type. For example, if your page is products.php?id=123 then run settype($id, "integer") in the script, before getting the product info from the database. If the user enters a non-numeric value in the url -- either pasting it wrong or intentionally :) -- the $id will be set to zero and database query will have no errors.

PHP settype note #25

This settype() behaviour seems consistent to me. Quoting two sections from the manual:

"When casting from a scalar or a string variable to an array, the variable will become the first element of the array: "
<pre>
2 $var = 'ciao';
3 $arr = (array) $var;
4 echo $arr[0];  // outputs 'ciao'
</pre>

And if (like your code above) you do a settype on an empty variable, you'll end up with a one element array with an empty (not unset!) first element. So appeanding to it will start appending at index 1. As for why reset() doesn't do anything:

"When you assign a value to an array variable using empty brackets, the value will be added onto the end of the array."

It doesn't matter where the array counter is; values are added at the end, not at the counter.