How do you change a text variable to an int in PHP?

Question

I have a variable that is definited by a POST call from a form where it is inputed into a text field. Is there any way to convert this variable to an interger?

From the form:

Lenght: <input name="length" value="10" type="text" id="lenght" size="2" />

From the php code:

$length = $_POST['lenght'];
$url = substr($url, 0, $length);

This doesn't seem to work and the only reason why I think it isn't working is because $lenght is defined as text and not an interger.

Answer 1

Seems to be a spelling error in your code: length vs. lenght - that could be your problem right there.

To do an explicit conversion, use the intval() function

$length = intval($_POST['length']);

Answer 2

It likely doesn't work because you misspelled length twice, instead of zero or three times.

Answer 3

Two things:

1. It doesn't work because you misspelled length <-> lenght

2. The correct way to convert a string to an integer is using the function intval.

---

$length = intval($_POST['length']);
$url = substr($url, 0, $length);

Answer 4

If you are sure that the value you are looking at has a correct representation for the type you want to convert to, you can also use a vanilla type cast operation:

$int = (int) "1"; // var_dump($int) => int(1)
$float = (float) "1.2345"; // var_dump($float) => float(1.2345)

Beware of incorrect representations of the variable that you are converting though, i.e casting "a random string" to a number might not yield the results you expect. If you are handling user input, you're better of using the above suggested solutions with function calls such as intval and floatval

Answer 5

Ignoring the misspellings of 'length' above, there are a few ways to explicitly convert a string into an integer in PHP. Usually this conversion will happen automatically. Take the following code:

$numeric_string = '42';
echo ($numeric_string * 2);

This will print out "84", as expected. See the reference on Type-Juggling.

If you KNOW that the string you have is a number (perhaps by checking is_numeric()) then you can either cast the variable to an Integer

$numeric_string = '42';
$converted_integer = (int) $numeric_string;
// or
$converted_integer = (integer) $numeric_string;

or use intval()

$numeric_string = '42';
$converted_integer = intval($numeric_string);

An important point to remember about intval() is that it will return a 0 if it can't resolve the string into an Integer. This could (potentially) give you a second way to check for errors (after is_numeric()), or it could cause unexpected results if you aren't properly insuring that the variable is numeric to begin with.