SunshinePHP Developer Conference 2015

Tür Dönüşümü

PHP değişken bildiriminde tür tanımlamayı gerektirmez (veya desteklemez); bir değişkenin türü kullanıldığı bağlama göre saptanır. Yani, string türünde bir değer $var değişkenine atanırsa $var, string türünde bir değişken haline gelir. $var değişkenine bir integer değer atanırsa $var, integer türünde bir değişken haline gelir.

Toplama işleci '+', PHP'nin özdevinimli tür dönüşümüne iyi bir örnektir. Bir toplama işleminde terimlerden biri float türündeyse her iki terim float olarak ele alınır ve sonuç float türünde olur. Aksi takdirde, terimler integer olarak yorumlanır ve sonuç integer türünde olur. Yalnız dikkat edin, bu işlem ne terimlerin kendi türlerini ne de ifadenin kendi türünü değiştirir.

<?php
$foo 
"0";  // $foo string türündedir (ASCII 48)
$foo += 2;   // $foo integer türündedir (2)
$foo $foo 1.3;  // $foo float türündedir (3.3)
$foo "10 Little Piggies"// $foo integer türündedir (15)
$foo "10 Small Pigs";     // $foo integer türündedir (15)
?>

Eğer yukarıdaki son iki örnek size tuhaf geldiyse Dizgelerin sayıya dönüşümü konusuna bakınız.

Bir değişkeni belli bir türe dönüşmeye zorlamak istiyorsanız Tür Çarpıtma konusuna bakınız. Bir değişkenin türünü değiştirmek istiyorsanız settype() işlevine bakınız.

Bu bölümdeki örnekleri sınamak için var_dump() işlevini kullanınız.

Bilginize:

array türüne özdevinimli dönüşüm şimdilik tanımsızdır.

Ayrıca, PHP dizgelerde konumlar üzerinden indislemeyi dizi indislemede kullanılan sözdizimiyle desteklediğinden aşağıdaki örnek tüm PHP sürümleri için geçerli bir örnektir:

<?php
$a    
'car'// $a string türündedir
$a[0] = 'b';   // $a hala string türündedir
echo $a;       // -> bar
?>

Daha fazla bilgi edinmek için Karakterinden dizgeye erişim konusuna bakınız.

Tür Çarpıtma

PHP'de tür çarpıtma (type casting) C'deki gibi çalışır: İstenen türün ismi parantez içinde türü çarpıtılacak değişkenin önüne yazılır.

<?php
$foo 
10;               // $foo integer türündedir
$bar = (boolean) $foo;   // $bar boolean türündedir
?>

İzin verilen çarpıtmalar:

  • (int), (integer) - integer türüne dönüşüm
  • (bool), (boolean) - boolean türüne dönüşüm
  • (float), (double), (real) - float türüne dönüşüm
  • (string) - string türüne dönüşüm
  • (array) - array türüne dönüşüm
  • (object) - object türüne dönüşüm
  • (unset) - NULL'a dönüşüm (PHP 5)

(binary) çarpıtması ve b önekinin ileriye dönük desteği PHP 5.2.1'de eklenmiştir.

Parantezler içinde sekmelere ve boşluklara izin verildiğinden aşağıdaki iki deyim eşdeğerdir:

<?php
$foo 
= (int) $bar;
$foo = ( int ) $bar;
?>

Normal dizgelerin ikil dizgelere dönüştürülmesi:

<?php
$binary 
= (binary) $string;
$binary b"ikil dizge";
?>

Bilginize:

Bir değişkenin türünü string türüne çarpıtmak yerine değişkeni çift tırnak içine almak aynı sonucu sağlar:

<?php
$foo 
10;            // $foo integer türündedir
$str "$foo";        // $str string türündedir
$fst = (string) $foo// $fst de string türündedir

// Bu, "bunlar aynı" basar
if ($fst === $str) {
    echo 
"bunlar aynı";
}
?>

Belli türler arasında çarpıtma yapılırken tam olarak ne olup bittiği açıkça belli olmayabilir. Daha fazla bilgi için şu bölümlere bakınız:

add a note add a note

User Contributed Notes 30 notes

up
13
Raja
9 years ago
Uneven division of an integer variable by another integer variable will result in a float by automatic conversion -- you do not have to cast the variables to floats in order to avoid integer truncation (as you would in C, for example):

$dividend = 2;
$divisor = 3;
$quotient = $dividend/$divisor;
print $quotient; // 0.66666666666667
up
8
Anonymous
12 years ago
Printing or echoing a FALSE boolean value or a NULL value results in an empty string:
(string)TRUE //returns "1"
(string)FALSE //returns ""
echo TRUE; //prints "1"
echo FALSE; //prints nothing!
up
7
yury at krasu dot ru
11 years ago
incremental operator ("++") doesn't make type conversion from boolean to int, and if an variable is boolean and equals TRUE than after ++ operation it remains as TRUE, so:

$a = TRUE;
echo ($a++).$a;  // prints "11"
up
6
ieee at REMOVE dot bk dot ru
2 years ago
There are some shorter and faster (at least on my machine) ways to perform a type cast.
<?php
$string
='12345.678';
$float=+$string;
$integer=0|$string;
$boolean=!!$string;
?>
up
6
philip_snyder at hotmail dot com
10 years ago
Re: the typecasting between classes post below... fantastic, but slightly flawed. Any class name longer than 9 characters becomes a problem... SO here's a simple fix:

function typecast($old_object, $new_classname) {
  if(class_exists($new_classname)) {
    // Example serialized object segment
    // O:5:"field":9:{s:5:...   <--- Class: Field
    $old_serialized_prefix  = "O:".strlen(get_class($old_object));
    $old_serialized_prefix .= ":\"".get_class($old_object)."\":";

    $old_serialized_object = serialize($old_object);
    $new_serialized_object = 'O:'.strlen($new_classname).':"'.$new_classname . '":';
    $new_serialized_object .= substr($old_serialized_object,strlen($old_serialized_prefix));
   return unserialize($new_serialized_object);
  }
  else
   return false;
}

Thanks for the previous code. Set me in the right direction to solving my typecasting problem. ;)
up
3
jphansen at uga dot edu
3 years ago
Type casting from string to int and vice versa is probably the most common conversation. PHP does this very simply through the +. and .= operators, removing any explicit casting:

<?php
$x
= 1;
var_dump($x); // int(1)
$x .= 1;
var_dump($x); // string(2) "11"; also an empty string ("") would cast to string without changing $x

$x = "1";
var_dump($x);  // string(1) "1"
$x += 1;
var_dump($x); // int(2); also a zero value (0) would cast to int without changing $x
?>
up
3
martinscotta at gmail dot com
4 years ago
in response to bhsmither at gmail.com

It raises a warning because of the bad enquoted variable

<?php

error_reporting
( E_ALL | E_STRICT );

$foo['ten'] = 10;        // $foo['ten'] is an array holding an integer at key "ten"
$str = "{$foo['ten']}"// works "10"
$str = "$foo[ten]";      // DO NOT work!
up
2
tom5025_ at hotmail dot com
10 years ago
function strhex($string)
{
   $hex="";
   for ($i=0;$i<strlen($string);$i++)
       $hex.=dechex(ord($string[$i]));
   return $hex;
}
function hexstr($hex)
{
   $string="";
   for ($i=0;$i<strlen($hex)-1;$i+=2)
       $string.=chr(hexdec($hex[$i].$hex[$i+1]));
   return $string;
}

to convert hex to str and vice versa
up
2
fardelian
1 year ago
Casting objects to arrays is a pain. Example:

<?php

class MyClass {

    private
$priv = 'priv_value';
    protected
$prot = 'prot_value';
    public
$pub = 'pub_value';
    public
$MyClasspriv = 'second_pub_value';

}

$test = new MyClass();
echo
'<pre>';
print_r((array) $test);

/*
Array
(
    [MyClasspriv] => priv_value
    [*prot] => prot_value
    [pub] => pub_value
    [MyClasspriv] => second_pub_value
)
*/

?>

Yes, that looks like an array with two keys with the same name and it looks like the protected field was prepended with an asterisk. But that's not true:

<?php

foreach ((array) $test as $key => $value) {
   
$len = strlen($key);
    echo
"{$key} ({$len}) => {$value}<br />";
    for (
$i = 0; $i < $len; ++$i) {
        echo
ord($key[$i]) . ' ';
    }
    echo
'<hr />';
}

/*
MyClasspriv (13) => priv_value
0 77 121 67 108 97 115 115 0 112 114 105 118
*prot (7) => prot_value
0 42 0 112 114 111 116
pub (3) => pub_value
112 117 98
MyClasspriv (11) => second_pub_value
77 121 67 108 97 115 115 112 114 105 118
*/

?>

The char codes show that the protected keys are prepended with '\0*\0' and private keys are prepended with '\0'.__CLASS__.'\0' so be careful when playing around with this.
up
2
post_at_henribeige_dot_de
11 years ago
If you want to do not only typecasting between basic data types but between classes, try this function. It converts any class into another. All variables that equal name in both classes will be copied.

function typecast($old_object, $new_classname) {
  if(class_exists($new_classname)) {
    $old_serialized_object = serialize($old_object);
    $new_serialized_object = 'O:' . strlen($new_classname) . ':"' . $new_classname . '":' .
                             substr($old_serialized_object, $old_serialized_object[2] + 7);
    return unserialize($new_serialized_object);
  }
  else
    return false;
}

Example:

class A {
  var $secret;
  function A($secret) {$this->secret = $secret;}
  function output() {echo("Secret class A: " . $this->secret);}
}

class B extends A {
  var $secret;
  function output() {echo("Secret class B: " . strrev($this->secret));}
}

$a = new A("Paranoia");
$b = typecast($a, "B");

$a->output();
$b->output();
echo("Classname \$a: " . get_class($a) . "Classname \$b: " . get_class($b));

Output of the example code above:

Secret class A: Paranoia
Secret class B: aionaraP
Classname $a: a
Classname $b: b
up
2
Anonymous
3 years ago
Checking for strings to be integers?
How about if a string is a float?

<?php

/* checks if a string is an integer with possible whitespace before and/or after, and also isolates the integer */
$isInt=preg_match('/^\s*([0-9]+)\s*$/', $myString, $myInt);

echo
'Is Integer? ',  ($isInt) ? 'Yes: '.$myInt[1] : 'No', "\n";

/* checks if a string is an integer with no whitespace before or after  */
$isInt=preg_match('/^[0-9]+$/', $myString);

echo
'Is Integer? ',  ($isInt) ? 'Yes' : 'No', "\n";

/* When checking for floats, we assume the possibility of no decimals needed.  If you MUST require decimals (forcing the user to type 7.0 for example) replace the sequence:
[0-9]+(\.[0-9]+)?
with
[0-9]+\.[0-9]+
*/

/* checks if a string is a float with possible whitespace before and/or after, and also isolates the number */
$isFloat=preg_match('/^\s*([0-9]+(\.[0-9]+)?)\s*$/', $myString, $myNum);

echo
'Is Number? ',  ($isFloat) ? 'Yes: '.$myNum[1] : 'No', "\n";

/* checks if a string is a float with no whitespace before or after */
$isInt=preg_match('/^[0-9]+(\.[0-9]+)?$/', $myString);

echo
'Is Number? ',  ($isFloat) ? 'Yes' : 'No', "\n";

?>
up
1
hemi68 at hotmail dot com
3 years ago
Cast a string to binary using PHP < 5.2.1

$binary = unpack('c*', $string);
up
2
Anonymous
9 years ago
If you have a boolean, performing increments on it won't do anything despite it being 1.  This is a case where you have to use a cast.

<html>
<body> <!-- don't want w3.org to get mad... -->
<?php
$bar
= TRUE;
?>
I have <?=$bar?> bar.
<?php
$bar
++;
?>
I now have <?=$bar?> bar.
<?php
$bar
= (int) $bar;
$bar++;
?>
I finally have <?=$bar?> bar.
</body>
</html>

That will print

I have 1 bar.
I now have 1 bar.
I finally have 2 bar.
up
1
miracle at 1oo-percent dot de
8 years ago
If you want to convert a string automatically to float or integer (e.g. "0.234" to float and "123" to int), simply add 0 to the string - PHP will do the rest.

e.g.

$val = 0 + "1.234";
(type of $val is float now)

$val = 0 + "123";
(type of $val is integer now)
up
1
rmirabelle
4 years ago
The object casting methods presented here do not take into account the class hierarchy of the class you're trying to cast your object into.

/**
     * Convert an object to a specific class.
     * @param object $object
     * @param string $class_name The class to cast the object to
     * @return object
     */
    public static function cast($object, $class_name) {
        if($object === false) return false;
        if(class_exists($class_name)) {
            $ser_object     = serialize($object);
            $obj_name_len     = strlen(get_class($object));
            $start             = $obj_name_len + strlen($obj_name_len) + 6;
            $new_object      = 'O:' . strlen($class_name) . ':"' . $class_name . '":';
            $new_object     .= substr($ser_object, $start);
            $new_object     = unserialize($new_object);
            /**
             * The new object is of the correct type but
             * is not fully initialized throughout its graph.
             * To get the full object graph (including parent
             * class data, we need to create a new instance of
             * the specified class and then assign the new
             * properties to it.
             */
            $graph = new $class_name;
            foreach($new_object as $prop => $val) {
                $graph->$prop = $val;
            }
            return $graph;
        } else {
            throw new CoreException(false, "could not find class $class_name for casting in DB::cast");
            return false;
        }
    }
up
1
edgar dot klerks at gmail dot com
5 years ago
It seems (unset) is pretty useless. But for people who like to make their code really compact (and probably unreadable). You can use it to use an variable and unset it on the same line:

Without cast:

<?php

$hello
= 'Hello world';
print
$hello;
unset(
$hello);

?>

With the unset cast:

<?php

$hello
= 'Hello world';
$hello = (unset) print $hello;

?>

Hoorah, we lost another line!
up
1
hek at theeks dot net
6 years ago
It would be useful to know the precedence (for lack of a better word) for type juggling.  This entry currently explains that "if either operand is a float, then both operands are evaluated as floats, and the result will be a float" but could (and I think should) provide a hierarchy that indicates, for instance, "between an int and a boolean, int wins; between a float and an int, float wins; between a string and a float, string wins" and so on (and don't count on my example accurately capturing the true hierarchy, as I haven't actually done the tests to figure it out).  Thanks!
up
1
namaroulis at gmail dot com
3 years ago
I found it tricky to check if a posted value was an integer.

<?php

$_POST
['a'] = "42";

is_int( $_POST['a'] ); //false
is_int( intval( "anything" ) ); //always true
?>

A method I use for checking if a string represents an integer value.

<?php
function check_int( $str )
                {
                    return 
is_numeric( $str ) && intval( $str ) - $str == 0;
                }
?>
up
1
Eric Lavoie
18 days ago
(array) null
array(null)

are not the same.

var_dump((array) null) =>
array (size=0)
  empty

var_dump(array (null)) =>
array (size=1)
  0 => null
up
1
kuzawinski dot marcin at NOSPAM dot gmail dot com
3 months ago
You REALLY must be aware what you are doing, when you cast a lot  in your code. For example, you can accidentaly change FALSE to TRUE  (probably not in one line, like here):

if(TRUE === (boolean) (array) (int) FALSE) {
    kaboom();
}
up
0
Anonymous
2 years ago
namaroulis stated "I found it tricky to check if a posted value was an integer"; to test if a variable is a number or a numeric string (such as form input, which is always a string), you must use is_numeric():

<?php
$_POST
['a'] = "42";

is_numeric( $_POST['a'] ); // true
?>
up
0
bhsmither at gmail.com
4 years ago
<?php
$foo
['ten'] = 10;            // $foo['ten'] is an array holding an integer at key "ten"
$str = "$foo['ten']";        // throws T_ENCAPSED_AND_WHITESPACE error
$str = "$foo[ten]";          // works because constants are skipped in quotes
$fst = (string) $foo['ten']; // works with clear intention
?>
up
0
kajsunansis at that gmail
5 years ago
json_decode users consider this, when casting stdClass to array:
<?php
$obj
= new stdClass();
$obj->{"2"} = "id";
$arr = (array) $obj;
$result = isset($arr["2"]) || array_key_exists(2, $arr); // false
?>
..though casting is at least 2x faster than foreach.
up
0
wbcarts at juno dot com
6 years ago
WHERE'S THE BEEF?

Looks like type-casting user-defined objects is a real pain, and ya gotta be nuttin' less than a brain jus ta cypher-it. But since PHP supports OOP, you can add the capabilities right now. Start with any simple class.
<?php
class Point {
  protected
$x, $y;

  public function
__construct($xVal = 0, $yVal = 0) {
   
$this->x = $xVal;
   
$this->y = $yVal;
  }
  public function
getX() { return $this->x; }
  public function
getY() { return $this->y; }
}

$p = new Point(25, 35);
echo
$p->getX();      // 25
echo $p->getY();      // 35
?>
Ok, now we need extra powers. PHP gives us several options:
  A. We can tag on extra properties on-the-fly using everyday PHP syntax...
    $p->z = 45; // here, $p is still an object of type [Point] but gains no capability, and it's on a per-instance basis, blah.
  B. We can try type-casting it to a different type to access more functions...
    $p = (SuperDuperPoint) $p; // if this is even allowed, I doubt it. But even if PHP lets this slide, the small amount of data Point holds would probably not be enough for the extra functions to work anyway. And we still need the class def + all extra data. We should have just instantiated a [SuperDuperPoint] object to begin with... and just like above, this only works on a per-instance basis.
  C. Do it the right way using OOP - and just extend the Point class already.
<?php
class Point3D extends Point {
  protected
$z;                                // add extra properties...

 
public function __construct($xVal = 0, $yVal = 0, $zVal = 0) {
   
parent::__construct($xVal, $yVal);
   
$this->z = $zVal;
  }
  public function
getZ() { return $this->z; }  // add extra functions...
}

$p3d = new Point3D(25, 35, 45);  // more data, more functions, more everything...
echo $p3d->getX();               // 25
echo $p3d->getY();               // 35
echo $p3d->getZ();               // 45
?>
Once the new class definition is written, you can make as many Point3D objects as you want. Each of them will have more data and functions already built-in. This is much better than trying to beef-up any "single lesser object" on-the-fly, and it's way easier to do.
up
0
lucazd at gmail dot com
6 years ago
@alexgr (20-Jun-2008)

Correct me if I'm wrong, but that is not a cast, it might be useful sometimes, but the IDE will not reflect what's really happening:

<?php
class MyObject {
   
/**
     * @param MyObject $object
     * @return MyObject
     */
   
static public function cast(MyObject $object) {
        return
$object;
    }
   
/** Does nothing */
   
function f() {}
}

class
X extends MyObject {
   
/** Throws exception */
   
function f() { throw new exception(); }
}

$x = MyObject::cast(new X);
$x->f(); // Your IDE tells 'f() Does nothing'
?>

However, when you run the script, you will get an exception.
up
0
alexgr at gmail dot com
6 years ago
For a Cast to a User Defined Object you can define a cast method:

class MyObject {
    /**
     * @param MyObject $object
     * @return MyObject
     */
    static public function cast(MyObject $object) {
        return $object;
    }
}

In your php page code you can:
$myObject = MyObject::cast($_SESSION["myObject"]);

Then, PHP will validate the value and your IDE will help you.
up
0
toma at smartsemantics dot com
9 years ago
In my much of my coding I have found it necessary to type-cast between objects of different class types.

More specifically, I often want to take information from a database, convert it into the class it was before it was inserted, then have the ability to call its class functions as well.

The following code is much shorter than some of the previous examples and seems to suit my purposes.  It also makes use of some regular expression matching rather than string position, replacing, etc.  It takes an object ($obj) of any type and casts it to an new type ($class_type).  Note that the new class type must exist:

function ClassTypeCast(&$obj,$class_type){
    if(class_exists($class_type,true)){
        $obj = unserialize(preg_replace"/^O:[0-9]+:\"[^\"]+\":/i",
          "O:".strlen($class_type).":\"".$class_type."\":", serialize($obj)));
    }
}
up
0
dimo dot vanchev at bianor dot com
10 years ago
For some reason the code-fix posted by philip_snyder at hotmail dot com [27-Feb-2004 02:08]
didn't work for me neither with long_class_names nor with short_class_names. I'm using PHP v4.3.5 for Linux.
Anyway here's what I wrote to solve the long_named_classes problem:

<?php
function typecast($old_object, $new_classname) {
    if(
class_exists($new_classname)) {
       
$old_serialized_object = serialize($old_object);
       
$old_object_name_length = strlen(get_class($old_object));
       
$subtring_offset = $old_object_name_length + strlen($old_object_name_length) + 6;
       
$new_serialized_object  = 'O:' . strlen($new_classname) . ':"' . $new_classname . '":';
       
$new_serialized_object .= substr($old_serialized_object, $subtring_offset);
        return
unserialize($new_serialized_object);
     } else {
         return
false;
     }
}
?>
up
-2
nullhilty at gmail dot com
6 years ago
Just a little experiment on the (unset) type cast:

<?php
$var
= 1;
$var_unset = (unset) $var;
$var_ref_unset &= (unset) $var;
var_dump($var);
var_dump($var_unset);
var_dump($var_ref_unset);
?>

output:
int(1)
NULL
int(0)
up
-4
Jeffrey
5 years ago
IMAGINATION REQUIRED...

We can be a witness to PHP's 'type-jugglin' in real-time with a simple implementation of a MemoryMap. For the sake our purposes, pretend that this is an empty MemoryMap.
+-------+------+------+-------+
| index | $var | type | value |
+-------+------+------+-------+
|     1 |  --- | NULL |  null |
|     2 |  --- | NULL |  null |
|     3 |  --- | NULL |  null |
|     4 |  --- | NULL |  null |
+-------+------+------+-------+

<?php
# create some variables...
$a = 10;
$b = "Hello";
$c = array(55.45, 98.65);
# Now look at map...
?>
+-------+-------+---------+--------+
| index |  $var |    type |  value |
+-------+-------+---------+--------+
|     1 |    $a | INTEGER |     10 |
|     2 |    $b |  STRING |  Hello |
|     3 | $c[0] |   FLOAT |  55.45 |
|     4 | $c[1] |   FLOAT |  98.65 |
+-------+-------+---------+--------+
<?php
# Now, change the variable types...
$a = "Bye";
$b = 2;
$c[0] = "Buy";
$c[1] = "Now!";
#Look at map...
?>
+-------+-------+---------+--------+
| index |  $var |    type |  value |
+-------+-------+---------+--------+
|     1 |    $a |  STRING |    Bye | <- used to be INTEGER
|     2 |    $b | INTEGER |      2 | <- used to be STRING
|     3 | $c[0] |  STRING |    Buy | <- used to be FLOAT
|     4 | $c[1] |  STRING |  Right | <- used to be FLOAT
+-------+-------+---------+--------+
To Top