How can you convert a text string to a numerical value in PHP for calculation purposes?

When converting a text string to a numerical value in PHP for calculation purposes, you can use the `intval()` function to convert the string to an integer or `floatval()` function to convert it to a float. These functions will strip any non-numeric characters from the string and return the numerical value for calculations.

$text = "123.45";
$numeric_value = floatval($text);
echo $numeric_value; // Output: 123.45