Question

Im trying to make a preg-replace pattern to convert the text “orderId” into “order-id”.

$argumentName = "orderId";
$argumentName = preg_replace("/([A-Z])/e", "-strtolower($1)", $argumentName);
echo $argumentName;

The output for this line is “order0d”. Why is this not working?

Answer 1

Since you’re specifying that your replacement-string is an expression, this:

strtolower($1)

is 'i' (as it should be), and this:

-strtolower($1)

is -'i' (“negative 'i'“), which forces the string 'i' to be interpreted as a number — 0.

What you want is

$argumentName = preg_replace("/([A-Z])/e", "'-' . strtolower($1)", $argumentName);

which concatenates the strings '-' and 'i'.