Variable Types
PHP supports eight primitive types.
Four scalar types:
- boolean : expresses truth value, TRUE or FALSE. Any non zero values and
non empty string are also counted as TRUE.
- integer : round numbers (-5, 0, 123, 555, ...)
- float : floating-point number or 'double' (0.9283838, 23.0, ...)
- string : "Hello World", 'PHP and MySQL, etc
Two compound types:
And finally two special types:
- resource ( one example is the return value of mysql_connect()
function)
- NULL
In PHP an array can have numeric key, associative key
or both. The value of an array can be of any type. To create an array use
the array() language construct like this.
<?php
$numbers = array(1, 2, 3, 4, 5, 6);
$age = array("mom" => 45, "pop" => 50, "bro"
=> 25);
$mixed = array("hello" => "World", 2 => "It's
two";
echo "numbers[4] = {$numbers[4]} <br>";
echo "My mom's age is {$age['mom']} <br>";
echo "mixed['hello'] = {$mixed['hello']} <br>";
echo "mixed[2] = {$mixed[2'}";
?>
When working with arrays there is one function I often used. The print_r()
function. Given an array this function will print the values in a format that
shows keys and elements
<?php
$myarray = array(1, 2, 3, 4, 5);
$myarray[5] = array("Hi", "Hello", "Konnichiwa",
"Apa Kabar");
echo '<pre>';
print_r($myarray);
echo '</pre>';
?>
Don't forget to print the preformatting tag <pre>
and </pre> before and after calling print_r().
If you don't use them then you'll have to view the page source to see a result
in correct format.
Type Juggling
In PHP you don't need to explicitly specify a type for variables. A variable's
type is determined by the context in which that variable is used. That is
to say, if you assign a string value to variable $var,
$var becomes a string. If you then assign an
integer value to $var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'.
If any of the operands is a float, then all operands are evaluated as floats,
and the result will be a float. Otherwise, the operands will be interpreted
as integers, and the result will also be an integer. Note that this does NOT
change the types of the operands themselves; the only change is in how the
operands are evaluated.
Example :
<?php
$myvar = "0"; // $myvar is string (ASCII 48)
$myvar += 2; // $myvar is now an integer (2)
$myvar = $foo + 1.3; // $myvar is now a float (3.3)
$myvar = 5 + "10 Piglets"; // $foo is integer (15)
?>
Type Casting
To cast a variable write the name of the desired type in parentheses before
the variable which is to be cast.
<?php
$abc = 10; // $abc is an integer
$xyz = (boolean) $abc; // $xyz is a boolean
echo "abc is $abc and xyz is $xyz <br>";
?>
- (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
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Tutorials 
