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Data Types

The PHP data types are: boolean, integer, float, string, array, object, resource, null PHP will auto-identify the data type if the author chooses not to declare the data type when creating a variable. boolean - represents either true(1) or false(0, null) $alive = true; // let php decide $alive = (boolean) true; // explicit data type declaration $alive = (boolean) "1"; // type cast a string to a boolean $alive = (boolean) 1; // type cast an integer to a boolean integer - positive/negative whole number $n = 3; // let php decide $n = (integer) 3; // explicit data type declaration $n = (integer) "3"; // type cast a string to an integer float - floating point number $price = 5.99; // let php decide $price = (float) 5.99; // explicit data type declaration $price = (float) "5.99"; // type cast a string or integer to a float string - any possible letters, numbers or symbols wrapped in quotes $str = "There are 12 in a dozen."; // let php decide $str = (string) "There are 12 in a dozen."; // explicit data type declaration $str = (string) 12; // type cast an integer to a string array - container for compartmentalizing data $arr = array('Joe', 23 , 'USA', true); echo serialize($arr); // a:4:{i:0;s:3:"Joe";i:1;i:23;i:2;s:3:"USA";i:3;b:1;} echo print_r($arr); // Array ( [0] => Joe [1] => 23 [2] => USA [3] => 1 ) 1 object - establishing a new object instance $myobj = new myobj(); resource - reference to an external resource or document $con = mysqli_connect(); echo get_resource_type($con); null - value for missing, empty, or unset variables. If null... it has no value and is not set. $var1 = NULL; // Casting a variable to null will remove the variable and unset its value

Get Data Type

$n = 3; echo gettype($n); // integer $country = "United States"; echo gettype($country); // string

Check Data Type

PHP has functions to test whether or not a variable is a certain "type". This is known as the is_* function family. <?php // set the variable and its value $myvar = "My phone number is 555-5555."; // Run a conditional statement to see if it is a string or not if (is_string($myvar)) { echo "Yes"; } else { echo "No"; } ?>

Type Casting

Authors can convert data from one type to another. It is called "type casting". An integer can be cast as a string, a string can be cast as an integer, a string or integer can be cast as a boolean, and so on. Examples are shown in the code examples above.



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