Casting PHP Variable Types

Nov 14, 2019PHP

PHP offers Type Juggling, which converts a variable to the chosen type. In the past, I never found myself using this much. Now, as I work more in the backend, I’m discovering many practical uses for it.

The syntax specifies a variable type inside parenthesis:

$var = (int) "123";

Input Conversion

When dealing with values that come from somewhere outside your theme, you might find input or meta fields that aren’t using the desired type.

$input_string = "0123";
$number = (int) $input_string; // 123

$input_number = 401;
$string = (string) $input_number; // "401"

Now you can concatenate, calculate, or compare using the variable as needed.

Type Checking

Working with TypeScript has emphasized the importance of variable types. Javascript is full of weird typecasting bugs but TypeScript guards against this. In PHP, strict comparisons are considered a best practice.

For example, you might expected a plugin to return a string value, but it returns null instead when nothing is found. Your theme is expecting booleans whenever it checks for style options.

function pvd_get_style() {
	return "style"; // The plugin returns a string value.
}
$has_style = pvd_get_style(); // $has_style = "style"

// Strict check to see if a style value was returned:
if ( (bool) $has_style === true ) {
  // Style returned.
}

Here the $has_style check will be cast to a true value for this strict comparison, yet it will remain a string that can be used elsewhere in your code.