PHP bug while validating user name

Question

I'm building a website using PHP and I need to validate whether the name entered by the user is correct or not. Since JavaScript is client-side, I cannot completely rely on that, so here's my server-side function to validate the name of the user:

function validate_name($name) {
    $name = trim($name);  // only for the purpose of debugging <---- edited comment
    echo $name;
    if (strlen($name) <= 1) {
        return "small";
    } else if (has_numbers($name)) { 
        return "numbers";
    } else {
        return true;
    }
}

After this, I check the input and display result accordingly:

function final_check() {
    if (validate_name($_POST["first_name"]) == "small") {
        echo "<span class='error'>Your first name cannot be empty</span>";
        return false;
    } else if (validate_name($_POST["first_name"]) == "numbers") {
        echo "<span class='error'>Numbers are not allowed in your first name</span>";
        return false;
    }
    return true;
}

When I enter nothing in the first_name field, I get the empty error message; when I enter numbers, I get the numbers error message. However, when I do enter a valid name, it gives me the name empty error message.

Here's the post data:

Array
(
    [email] => [email protected]
    [first_name] => qwe
    [last_name] => wqe
    [password] => qwe
    [re_password] => qwe
    [gender] => Male
)

Output:

Your first name cannot be empty

Any idea what I am doing wrong? I have been stumped for the past hour trying to fix this and I haven't been able to find a solution.

Answer 1

Array
(
    [email] => [email protected]
    [first_name] => qwe
    [last_name] => wqe
    [password] => qwe
    [re_password] => qwe
    [gender] => Male
)

// First_name length = 3

function validate_name($name) {
    $name = trim($name);
    echo $name;
    if (strlen($name) <= 1) {
        return "small";
    } else if (has_numbers($name)) { 
        return "numbers";
    } else {
        return true;      // satisfy this case return true
    }
}

and here it's becoming like

function final_check() {
    if (validate_name($_POST["first_name"]) == "small") {   // if(1 == 'small')
        echo "<span class='error'>Your first name cannot be empty</span>";
        return false;
    } else if (validate_name($_POST["first_name"]) == "numbers") {
        echo "<span class='error'>Numbers are not allowed in your first name</span>";
        return false;
    }
    return true;
}

if(1 == 'small') its a string comparison with Boolean which always going to return true.

Please check this page in the manual to understand the problem.