Question

Question:

How do I check if a function is being passed as a parameter?

Especially if the function being passed is returning a string etc?

IE in the example below I don’t want to htmlentities the function html being passed as a parameter, but I do want to htmlentities anything else. Also assuming there could be more than a single parameter that needs to take a function later.

Example:

function html($tag,$content)
{

if(!is_callable($content)){$var=htmlentities($var, ENT_NOQUOTES, "UTF-8");}

return "<".$tag.">".$content."</".$tag.">";

}


echo html(html('Example','Example'),'Example');

This example does not seem to work for me. I still get htmlentitied content when its a function.

Answer 1

While you cannot detect if a string being passed to a function is the result of another function, you can pass something that is not a string, but behaves like a string.

While I don’t really recommend this, and the side-effects could be plentiful, here is a possible solution.

A helper class that pretends to be a string, but it’s a class.

class sillyString
{
    private $string = '';

    public function __construct($string)
    {
        $this->string = $string;
    }

    public function __toString()
    {
        return $this->string;
    }
}

Your function. I’ve jiggled it around a bit, but it checks the type of the content.

function html($content, $tag)
{
    if (!is_object($content)) {
        $content = htmlentities($content, ENT_NOQUOTES, "UTF-8");
    }

    return new sillyString("<".$tag.">".$content."</".$tag.">");
}

Call your function as before.

print html(html('content','tag1'),'tag2');

So the function can now tell that you haven’t passed a string, but you can still use it exactly like a string inside the function.