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Working With PHP Data Types


Using and manipulating variables in PHP is extremely easy because PHP includes several functions to help us compare and contrast them. In this article, Steve introduces us to the range of PHP data types. He also teaches us how to work with and manipulate PHP data types. This article also presents several code examples that you can test and learn from.

Author Info:
By: Steve Adcock
Rating: 4 stars4 stars4 stars4 stars4 stars / 16
January 23, 2002
TABLE OF CONTENTS:
  1. · Working With PHP Data Types
  2. · Defining variables and constants
  3. · Manipulating a variables data type
  4. · If this, if that
  5. · Conclusion

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Working With PHP Data Types - If this, if that
(Page 4 of 5 )

PHP's if statements can be used to check the validity of a variable, its integrity, or even the presence of data within a variable. Let's use PHP’s gettype function in our first example to check the data type of a variable:

<?

$i = 10;

if(gettype($i) == "integer") // Checks if variable i is an integer

{

echo("the variable $i is an integer"); // If integer, then display

} else {

echo("variable $i is not an integer"); // If not integer, then display

}

?>


Because we have given the $i variable a default value of ten, it is seen as an integer and the text "the variable $i is an integer" will be displayed using the echo function. Try changing 10 to 10.1. Because 10.1 is a double and not an integer, the second statement, "sorry, variable $i is not an integer" will be displayed instead.

Two more functions, isset and unset are also useful for working with data types. isset checks to see whether or not a value has been assigned to a variable. unset will destroy the variable and remove it from memory.

<?

$i = 10;

if(isset($i)) // Checks if variable i has a value

{

echo("variable $i has a value"); // If defined, then display

} else {

echo("variable $i has no value"); // If not integer, then display

}

?>


Since variable $i contains a value, the text "variable $i has a value" will be displayed. If we deleted the $i = 10; line, then the second echo statement displaying "variable $i has no value" will execute. Let's now take a look at the unset function, which allows us to remove a variable for memory:

<?

$i = 10;

unset($i); // Destroys variable $i

if(isset($i)) // Checks if variable $i has a value

{

echo("this should not display"); // If not destroyed, then display

}

?>


In the first part of this sample code, we have defined a new integer variable, $i. Next, we used the unset function and pass in $i as its only parameter, which destroys the variable. Just to make sure it has been destroyed, we use the isset function to check it for a value. Since it shouldn't contain a value, the echo statement will never be executed and we will be left with a blank page.

We can also perform an action if, and only if, a particular variable is a specific data type, by using PHP’s "is_[variable type]" set of functions including is_double, is_string, is_array, or is_integer to check whether a specific variable matches the data type we're after. Let's look at an example.

<?

$i = 10;

if (is_integer($i))

echo("$i is an integer");

if (is_string($i))

echo("$i is a string");

if (is_double($i))

echo("$i is a double");

?>


Since $i is an integer, the first if statement will evaluate to true, and "$i is an integer" will be displayed. Try adding quotes around the value of $i. The is_string function would evaluate to true, thus displaying "$I is a string".
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