How to force arguments to be integer/string

Question

I'd like my functions to expect strings/integers or throw a fit, like:

warning: preg_match() expects parameter 2 to be string

However for this function

public function setImage($target, $source_path, integer $width, integer $height){...

I get:

Argument 4 passed to My_Helper_Image::setImage() must be an instance of integer, integer given

But:

function(array $expectsArray)

works as I expect, how would I achieve the same effect as with integers and strings?

Big Update

PHP 7 now supports Scalar Type Hinting

function increment(int $number) {
     return $number++;
}

Answer 1

Scalar TypeHints are available as of PHP 7:

Scalar type declarations come in two flavours: coercive (default) and strict. The following types for parameters can now be enforced (either coercively or strictly): strings (string), integers (int), floating-point numbers (float), and booleans (bool). They augment the other types introduced in PHP 5: class names, interfaces, array and callable.

There is no Type Hints for scalars before PHP7. PHP 5.3.99 did have scalar typehints but it wasn't finalised at that point if they stay and how they will work then.

Nevertheless, there is options for enforcing scalar arguments before PHP7.

There is a couple of is_* functions that let you do that, e.g.

• is_int — Find whether the type of a variable is integer
• is_string — Find whether the type of a variable is string
• more

To raise a Warning, you'd use

• trigger_error — Generates a user-level error/warning/notice message

with an E_USER_WARNING for $errorType.

Example

function setInteger($integer)
{
    if (FALSE === is_int($integer)) {
        trigger_error('setInteger expected Argument 1 to be Integer', E_USER_WARNING);
    }
    // do something with $integer
}

Alternative

If you want to use Scalar Type Hints desperately, have a look at

• http://edorian.github.io/2010-03-30-typehints-hack-for-literal-values-in-php/

which shows a technique for enforcing scalar typehints via a custom Error Handler.