Typecasting in PHP
The meaning of type casting is to use the value of a variable with different data type. In other word typecasting is a way to utilize one data type variable into the different data type. Typecasting is the explicit conversion of data type because user explicitly defines the data type in which he wants to cast. In this tutorial, we will explore various aspects of PHP Type casting.
PHP does not require or support type definition of the variable. In PHP we never define data type while declaring the variable. In PHP variables automatically decide the data type on the basis of the value assignment or context. For example:
$i =1;
var_dump($i); //$i is integer
$i = 2.3;
var_dump($i); //$i is float
$i = "php type casting";
var_dump($i); //$i is string
?>
In above example, you can see that variable $i type is getting changed on the different type of value assignment. So due to this flexible nature of the PHP, we do not need to type cast variable always. But Sometimes when we need extra security in the variable we cast type. For example, if we are taking some integer input from user then we should type cast.
Type casting in PHP works same as C programming. Desired data type name with parenthesis before the variable which we need to cast. For example, if we need to cast the string to the integer then below will work:
$string_var = "string value for php type";
$int_var = (int)$string_var;
var_dump($int_var);
?>
We can cast following data type variable in PHP
- (int), (integer) — cast to integer
- (bool), (boolean) — cast to boolean
- (float), (double), (real) — cast to float
- (string) — cast to string
- (array) — cast to array
- (object) — cast to object
- (unset) — cast to NULL (PHP 5)
PHP type Casting to Integer
Using (int) or (integer) keyword we can cast/convert any data type value to the integer. If we need to take integer casting then we can also use intval() function.
If we will convert boolean to an integer then False will output 0 and true will output 1. For example
$bool_false = false;
$int_val = (int) $bool_false ;
var_dump($int_val); //Output will be 0
$bool_true = true;
$int_val = (int) $bool_true ;
var_dump($int_val); //Output will be 1
?>
If we will convert resource data type to an integer then it will return unique resource ID. For example
$fp = fopen("filename.txt", "w");
$int_cast = (int) $fp;
var_dump($int_cast);
?> If we will cast float number to an integer then the output will be the number before the decimal. Means if we will cast 10.9 to an integer then the output will be 10.
$float_num = 10.9;
echo (int) $float_num;
?>
Conversion from string to number is quite complected and also used rarely.
PHP type casting to Boolean
We can cast any variable to Boolean using the (bool) or (boolean) keyword. If we will convert any variable data type to Boolean then if the variable has value(and value is not 0) then it will return true, otherwise false.
var_dump((bool) 1); //return true
var_dump((bool) 0);//return false
var_dump((bool) "");//return false
var_dump((bool) "ank");//return true
?>
PHP type casting to Float
Except for the string, all float casting first go through integer casting then converted into the float. If we will convert an object to float then notice will be thrown in PHP 5.
PHP type casting to String
We can convert any data type to string using (string). String conversion automatically happens in the scope where it needed. In the most of the cases value not changed. But for boolean false converted into “” and true in “1”. Below is the example
$boo_true = true;
var_dump((string) $boo_true);// Output will be "1"
var_dump((string) false) ;//Output will be ""
var_dump((string) 1);//output will be 1
?>
PHP type casting to Array
We can convert any data type variable in an array using the (array) keyword. Any scalar data type conversion into the array will create an array and add the element at the 0th index. For example:
var_dump((array) 5);// value 5 in the array with 0th index
var_dump((array) NULL);// Will be empty array
?>
Usually, we use array conversion in the case of the object. All public property will convert to the key value format.
Php any type to string
Cast a string to binary using PHP < 5.2.1
I found it tricky to check if a posted value was an integer.
is_int ( $_POST [ ‘a’ ] ); //false
is_int ( intval ( «anything» ) ); //always true
?>
A method I use for checking if a string represents an integer value.
$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
?>
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:
$hello = ‘Hello world’ ;
print $hello ;
unset( $hello );
$hello = ‘Hello world’ ;
$hello = (unset) print $hello ;
?>
Hoorah, we lost another line!
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!
May be expected, but not stated ..
Casting to the existing (same) type has no effect.
$t = ‘abc’; // string ‘abc’
$u=(array) $t; // array 0 => string ‘abc’ $v=(array) $u; // array 0 => string ‘abc’
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:
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 );
$x -> f (); // Your IDE tells ‘f() Does nothing’
?>
However, when you run the script, you will get an exception.
In my much of my coding I have found it necessary to type-cast between objects of different class types.
More specifically, I often want to take information from a database, convert it into the class it was before it was inserted, then have the ability to call its class functions as well.
The following code is much shorter than some of the previous examples and seems to suit my purposes. It also makes use of some regular expression matching rather than string position, replacing, etc. It takes an object ($obj) of any type and casts it to an new type ($class_type). Note that the new class type must exist:
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.
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.
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 $p3d -> getZ (); // 45
?>
Once the new class definition is written, you can make as many Point3D objects as you want. Each of them will have more data and functions already built-in. This is much better than trying to beef-up any «single lesser object» on-the-fly, and it’s way easier to do.
Re: the typecasting between classes post below. fantastic, but slightly flawed. Any class name longer than 9 characters becomes a problem. SO here’s a simple fix:
function typecast($old_object, $new_classname) if(class_exists($new_classname)) // Example serialized object segment
// O:5:»field»:9: $old_serialized_prefix = «O:».strlen(get_class($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. 😉
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.
I have 1 bar.
I now have 1 bar.
I finally have 2 bar.
Checking for strings to be integers?
How about if a string is a float?
/* checks if a string is an integer with possible whitespace before and/or after, and also isolates the integer */
$isInt = preg_match ( ‘/^\s*(7+)\s*$/’ , $myString , $myInt );
echo ‘Is Integer? ‘ , ( $isInt ) ? ‘Yes: ‘ . $myInt [ 1 ] : ‘No’ , «\n» ;
/* checks if a string is an integer with no whitespace before or after */
$isInt = preg_match ( ‘/^7+$/’ , $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:
3+(\.1+)?
with
7+\.3+
*/
/* checks if a string is a float with possible whitespace before and/or after, and also isolates the number */
$isFloat = preg_match ( ‘/^\s*(5+(\.1+)?)\s*$/’ , $myString , $myNum );
echo ‘Is Number? ‘ , ( $isFloat ) ? ‘Yes: ‘ . $myNum [ 1 ] : ‘No’ , «\n» ;
/* checks if a string is a float with no whitespace before or after */
$isInt = preg_match ( ‘/^6+(\.1+)?$/’ , $myString );
echo ‘Is Number? ‘ , ( $isFloat ) ? ‘Yes’ : ‘No’ , «\n» ;