Data Types

PHP supports the following primitive data types:

• bool: a value that’s either true or false.
• int: a whole number value.
• float: a numeric value with decimal.
• string: a series of characters.
• array: an ordered map of key/value pairs.
• object: an instance of a pre-defined class.
• callable: a reference to a PHP function.
• iterable: represents any array or object implementing the Traversable interface.
• resource: a reference to an external resource.
• NULL: represents a variable with no value.

Rather than being declared in code, the data type is decided at runtime depending on the context. There are many ways to determine the type of a variable or expression.

Printing the Type and Value

The var_dump() function prints out the type and value of an expression.

Example

$text = "PHP";
var_dump($text);

The output looks like this:

string(3) "PHP"

The gettype() Function

The gettype() function returns a human readable string representing the data type of an expression.

Example

$text = "PHP";
echo(gettype($text));

Results in the output:

string

Checking Types

PHP has a number of “is_type” functions to check the type of a variable.

• is_bool($value) returns true if $value is a bool value.
• is_int($value) returns true if $value is an int value. (Also is_integer().)
• is_float($value) returns true if $value is a float value.
• is_string($value) returns true if $value is a string.
• is_array($value) returns true if $value is an array value.
• is_object($value) returns true if $value is an object value.
• is_iterable($value) returns true if $value is an iterable value.
• is_resource($value) returns true if $value is a resource value.
• is_null($value) returns true if $value is a NULL value.

The is_callable() function has a slightly more complicated syntax:

is_callable($value, $syntax_only, $callable_name)

Where $value is the value being checked. The $syntax_only parameter is an optional boolean flag that if set true will only check if $value is properly structured to be used as a callback. The $callable_name parameter is optional, and if included, will be set to the name of the callable function or method referred to by $value. The function will return true if $value is a callable value.

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