Php data types int

Types

The meaning of a value is determined by its type. PHP’s types are categorized as scalar types and composite types. The scalar types are Boolean, integer, floating point, string, and null. The composite types are array, and object. The resource is an opaque type whose internal structure is not specified and depends on the implementation.

The scalar types are value types. That is, a variable of scalar type behaves as though it contains its own value.

The composite types can contain other variables, besides the variable itself, e.g. array contains its elements and object contains its properties.

The objects and resources are handle types. The type contains information — in a handle — that leads to the value. The differences between value and handle types become apparent when it comes to understanding the semantics of assignment, and passing arguments to, and returning values from, functions.

Variables are not declared to have a particular type. Instead, a variable’s type is determined at runtime by the value it contains. The same variable can contain values of different types at different times.

Useful library functions for interrogating and using type information include gettype , is_type , settype , and var_dump .

Scalar Types

General

The integer and floating-point types are collectively known as arithmetic types. The library function is_numeric indicates if a given value is a number or a numeric string.

The library function is_scalar indicates if a given value has a scalar type. However, that function does not consider NULL to be scalar. To test for NULL , use is_null .

Some objects may support arithmetic and other scalar operations and/or be convertible to scalar types (this is currently available only to internal classes). Such object types together with scalar types are called scalar-compatible types. Note that the same object type may be scalar-compatible for one operation but not for another.

The Boolean Type

The Boolean type is bool , for which the name boolean is a synonym. This type is capable of storing two distinct values, which correspond to the Boolean values true and false , respectively. The internal representation of this type and its values is unspecified.

The library function is_bool indicates if a given value has type bool .

The Integer Type

There is one integer type, int , for which the name integer is a synonym. This type is binary, signed, and uses twos-complement representation for negative values. The range of values that can be stored is implementation-defined; however, the range [-2147483648, 2147483647], must be supported. This range must be finite.

Certain operations on integer values produce a mathematical result that cannot be represented as an integer. Examples include the following:

• Incrementing the largest value or decrementing the smallest value.
• Applying the unary minus to the smallest value.
• Multiplying, adding, or subtracting two values.

In such cases, the computation is done as though the types of the values were float with the result having that type.

The constants PHP_INT_SIZE , PHP_INT_MIN and PHP_INT_MAX define certain characteristics about type int .

The library function is_int indicates if a given value has type int .

The Floating-Point Type

There is one floating-point type, float , for which the names double and real are synonyms. The float type must support at least the range and precision of IEEE 754 64-bit double-precision representation.

The library function is_float indicates if a given value has type float . The library function is_finite indicates if a given floating-point value is finite. The library function is_infinite indicates if a given floating-point value is infinite. The library function is_nan indicates if a given floating-point value is a NaN .

The String Type

A string is a set of contiguous bytes that represents a sequence of zero or more characters.

Conceptually, a string can be considered as an array of bytes—the elements—whose keys are the int values starting at zero. The type of each element is string . However, a string is not considered a collection, so it cannot be iterated over.

A string whose length is zero is an empty string.

As to how the bytes in a string translate into characters is unspecified.

Although a user of a string might choose to ascribe special semantics to bytes having the value \0 , from PHP’s perspective, such null bytes have no special meaning. PHP does not assume strings contain any specific data or assign special values to any bytes or sequences. However, many library functions assume the strings they receive as arguments are UTF-8 encoded, often without explicitly mentioning that fact.

A numeric string is a string whose content exactly matches the pattern defined by the str-numeric production below. A leading-numeric string is a string whose initial characters follow the requirements of a numeric string, and whose trailing characters are non-numeric. A non-numeric string is a string that is not a numeric string.

str-numeric:: str-whitespaceopt signopt str-number str-whitespace:: str-whitespaceopt str-whitespace-char str-whitespace-char:: new-line Space character (0x20) Horizontal-tab character (0x09) Vertical-tab character (0x0B) Form-feed character (0x0C) str-number:: digit-sequence floating-literal 

Note that digit-sequence is interpreted as having base-10 (so «0377» is treated as 377 decimal with a redundant leading zero, rather than as octal 377).

Only one mutation operation may be performed on a string, offset assignment, which involves the simple assignment operator =.

The library function is_string indicates if a given value has type string.

The Null Type

The null type has only one possible value, NULL . The representation of this type and its value is unspecified.

The library function is_null indicates if a given value is NULL .

Composite Types

The Array Type

An array is a data structure that contains a collection of zero or more elements whose values are accessed through keys that are of type int or string . See more details in arrays chapter.

The library function is_array indicates if a given value is an array.

Objects

An object is an instance of a class. Each distinct class-declaration defines a new class type, and each class type is an object type. The representation of object types is unspecified.

The library function is_object indicates if a given value is an object, and the library function get_class indicates the name of an object’s class.

Resources

A resource is a descriptor to some sort of external entity. Examples include files, databases, and network sockets.

A resource is an abstract entity whose representation is unspecified. Resources are only created or consumed by the implementation; they are never created or consumed by PHP code.

Each distinct resource has a unique identity of some unspecified form.

The library function is_resource indicates if a given value is a resource, and the library function get_resource_type indicates the type of a resource.

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PHP Data Types

Variables can store data of different types, and different data types can do different things.

PHP supports the following data types:

• String
• Integer
• Float (floating point numbers — also called double)
• Boolean
• Array
• Object
• NULL
• Resource

PHP String

A string is a sequence of characters, like «Hello world!».

A string can be any text inside quotes. You can use single or double quotes:

Example

PHP Integer

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.

• An integer must have at least one digit
• An integer must not have a decimal point
• An integer can be either positive or negative
• Integers can be specified in: decimal (base 10), hexadecimal (base 16), octal (base 8), or binary (base 2) notation

In the following example $x is an integer. The PHP var_dump() function returns the data type and value:

Example

PHP Float

A float (floating point number) is a number with a decimal point or a number in exponential form.

In the following example $x is a float. The PHP var_dump() function returns the data type and value:

Example

PHP Boolean

A Boolean represents two possible states: TRUE or FALSE.

Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.

PHP Array

An array stores multiple values in one single variable.

In the following example $cars is an array. The PHP var_dump() function returns the data type and value:

Example

You will learn a lot more about arrays in later chapters of this tutorial.

PHP Object

Classes and objects are the two main aspects of object-oriented programming.

A class is a template for objects, and an object is an instance of a class.

When the individual objects are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties.

Let’s assume we have a class named Car. A Car can have properties like model, color, etc. We can define variables like $model, $color, and so on, to hold the values of these properties.

When the individual objects (Volvo, BMW, Toyota, etc.) are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties.

If you create a __construct() function, PHP will automatically call this function when you create an object from a class.

Example

class Car public $color;
public $model;
public function __construct($color, $model) $this->color = $color;
$this->model = $model;
>
public function message() return «My car is a » . $this->color . » » . $this->model . «!»;
>
>

$myCar = new Car(«black», «Volvo»);
echo $myCar -> message();
echo «
«;
$myCar = new Car(«red», «Toyota»);
echo $myCar -> message();
?>

PHP NULL Value

Null is a special data type which can have only one value: NULL.

A variable of data type NULL is a variable that has no value assigned to it.

Tip: If a variable is created without a value, it is automatically assigned a value of NULL.

Variables can also be emptied by setting the value to NULL:

Example

PHP Resource

The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.

A common example of using the resource data type is a database call.

We will not talk about the resource type here, since it is an advanced topic.

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Php data types int

While waiting for native support for typed arrays, here are a couple of alternative ways to ensure strong typing of arrays by abusing variadic functions. The performance of these methods is a mystery to the writer and so the responsibility of benchmarking them falls unto the reader.

PHP 5.6 added the splat operator (. ) which is used to unpack arrays to be used as function arguments. PHP 7.0 added scalar type hints. Latter versions of PHP have further improved the type system. With these additions and improvements, it is possible to have a decent support for typed arrays.

function typeArrayNullInt (? int . $arg ): void >

function doSomething (array $ints ): void (function (? int . $arg ) <>)(. $ints );
// Alternatively,
( fn (? int . $arg ) => $arg )(. $ints );
// Or to avoid cluttering memory with too many closures
typeArrayNullInt (. $ints );

function doSomethingElse (? int . $ints ): void /* . */
>

$ints = [ 1 , 2 , 3 , 4 , null ];
doSomething ( $ints );
doSomethingElse (. $ints );
?>

Both methods work with all type declarations. The key idea here is to have the functions throw a runtime error if they encounter a typing violation. The typing method used in doSomethingElse is cleaner of the two but it disallows having any other parameters after the variadic parameter. It also requires the call site to be aware of this typing implementation and unpack the array. The method used in doSomething is messier but it does not require the call site to be aware of the typing method as the unpacking is performed within the function. It is also less ambiguous as the doSomethingElse would also accept n individual parameters where as doSomething only accepts an array. doSomething’s method is also easier to strip away if native typed array support is ever added to PHP. Both of these methods only work for input parameters. An array return value type check would need to take place at the call site.

If strict_types is not enabled, it may be desirable to return the coerced scalar values from the type check function (e.g. floats and strings become integers) to ensure proper typing.

same data type and same value but first function declare as a argument type declaration and return int(7)
and second fucntion declare as a return type declaration but return int(8).

function argument_type_declaration(int $a, int $b) return $a+$b;
>

function return_type_declaration($a,$b) :int return $a+$b;
>

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