How do you determine the data type of a variable in PHP?
PHP is more tolerant than other programming languages and does not require a fixed data type to be specified for a variable. In fact, there is not even an opportunity to do so. Nevertheless, the value of each variable has a data type that influences the processing of this value. For example, adding integers behaves differently than adding strings.
gettype()
To find out what data type the value of a variable has, gettype($var) can be used. This function returns one of the following string, which correspond to the known data types in PHP: ‘boolean’, ‘integer’, ‘double’, ‘string’, ‘array’, ‘object’, ‘resource’, ‘NULL’, ‘unknown type’. Floats are represented by ‘double’.
<?php
function func($par) {
echo("Data type of '".$par."' is '".gettype($par)."'.\n");
}
func(50);
func(2.5);
func("hello");
func(null);
?>
Output:
Data type of '50' is 'integer'. Data type of '2.5' is 'double'. Data type of 'hello' is 'string'. Data type of '' is 'NULL'.
is_* functions
The function gettype() should only be used to output the datatype of a variable. Testing for special datatypes – with this function – is not recommended, because the returns may change at some point. Instead, the functions is_boolean($var), is_string($var), is_float($var), is_array($var), is_object($var), is_resource($var) and is_null($var) should be used.
<?php
function square($val)
{
// Only integers or floats should be squared by this function
// an error is thrown for all other data types.
if (!is_int($val) && !is_float($val))
{
throw new Exception('Invalid parameter passed. '
.'Integer was expected, '.gettype($val).' was given.');
}
return ($val * $val);
}
// square with 2 as a number
var_dump(square(2));
// square with 2 as a string, produces an error
try
{
var_dump(square("2"));
}
catch (Exception $e)
{
echo($e->getMessage());
}
?>
Output:
int(4) Invalid parameter passed. Integer was expected, string was given.
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