php - Compare 2 strings using empty and strcmp

Hello so I guess its simple. I need to check if the 2 given strings are empty then compare both strings using strcmp and have it call back to a function that would echo out a statement if they are a match or not. This is what I have

    $firstString = "Geek2Geek";
    $secondString = "Geezer2Geek";

    function sameVar($firstString, $secondString) {
        echo "Both strings similar";
    }

    function diffVar($firstString, $secondString) {
        echo "Both strings do not the same";
    }

    if (empty($firstString)) {
        echo "The first string is empty";
    } else {
        echo "The first string is not empty";
    }

    if (empty($secondString)) {
        echo "The second string is empty";
    } else {
        echo "The second string is not empty";
    }

    if (strcmp($firstString, $secondString) !== 0) {
        sameVar($firstString, $secondString);
    } else {
        diffVar($firstString, $secondString);
    } 

I created an if statement to check if the strings are empty, but I was wondering if there is a way to create one if statement to check if both strings are empty. I tried

if (empty($firstString, $secondString))

but then nothing appears when I reload the page. Also gives me a red dot in VSCode

I guess the second thing would be using strcmp and having it call the functions. I played around with it and deleting the value within $secondString and it still calls the function sameVar

EDIT:

Per the instructions, I had to have an if statement nested within the first if statement if checked that both strings were not empty. I got it done and its pretty much completed. I just need to figure out how to include an else clause at the end which executes if either the $firstString or $secondString contain an empty value.

My other issue is that either function does not echo out the complete sentence. It should echo "Both Geek2Geek and Geezer2Geek do not match" instead I get "Both and do not match"

   <?php

    $firstString = "Geek2Geek";
    $secondString = "Geezer2Geek";

    function sameVar() {
        echo "Both $firstString and $secondString match";
    }

    function diffVar() {
        echo "Both $firstString and $secondString do not match";
    }

    if (empty($firstString) && empty($secondString)) {
        echo "The Strings are empty";
    } else {
        echo "The Strings are not empty <br/>";

        if (strcmp($firstString, $secondString) === 0) {
            sameVar();
        }  else {
            diffVar();

            echo "<p>Either the $firstString variable and the $secondString variable does not contain a value so the two strings cannot be compared.</p>";
        }
    }

    // need to include
    // else { echo "<p>Either the $firstString variable and the      $secondString variable does not contain a value so the two strings cannot be compared. </p>" }
    // must be included at the end of the script 

?>

Solution:

As empty takes only one argument (manual), you can't use it like empty($firstString, $secondString).

So, if you wat to check if both string are empty, then your code is:

if (empty($firstString) && empty($secondString)) {
    echo 'Both string are empty';
}

Going further, this code

if (strcmp($firstString, $secondString) !== 0) {
    sameVar($firstString, $secondString);
} else {
    diffVar($firstString, $secondString);
}

must be rewritten as

if (strcmp($firstString, $secondString) === 0) {  // === instead of !==
    sameVar($firstString, $secondString);
} else {
    diffVar($firstString, $secondString);
}

because returns 0 only when strings are the same.

if (strcmp($firstString, $secondString) === 0) {
    sameVar();
} else {
    diffVar();
}

// where `sameVar` and `diffVar` are:
function sameVar() {
    echo "Both strings similar";
}

function diffVar() {
    echo "Both strings do not the same";
}

if (empty($firstString) && empty($secondString)) {

   ...
}

Also, you might want to read about logical operators.

Regarding strcmp, you just need to flip the function calls - !== 0 means both strings are not equal.