PHP bug while validating user name - php

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] => ewf#gmail.com
[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] => ewf#gmail.com
[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.

Answer 2

Your logic is correct, however, as other questions pointed out, string with boolean comparison will return true.
To fix this, you should use === instead of == and all should be fine

Answer 3

What I suggest here is to modify your validate_name function, so that it will have only one return type, since it can currently return either a string or a boolean, which is not a good practice.
For instance you can do something like :
function validate_name($name) {
$name = trim($name);
echo $name;
if (strlen($name) <= 1) {
return "small";
} else if (has_numbers($name)) {
return "numbers";
} else {
return "ok"; // or return ""; or whatever string you want.
}
}
Moreover to optimize your code and improve readability, you can change your final_check function so that there will be only one call to validate_name using a intermediate variabe.
function final_check() {
$valid = validate_name($_POST["first_name"]);
if ($valid == "small") {
echo "<span class='error'>Your first name cannot be empty</span>";
return false;
} else if ($valid == "numbers") {
echo "<span class='error'>Numbers are not allowed in your first name</span>";
return false;
}
return true;
}

Answer 4

try with
if (validate_name($_POST["first_name"]) == "small" && !validate_name($_POST["first_name"])) {
echo "<span class='error'>Your first name cannot be empty</span>";
return false;
} else if (validate_name($_POST["first_name"]) == "numbers" && validate_name($_POST["first_name"])) {
echo "<span class='error'>Numbers are not allowed in your first name</span>";
return false;
}
true == 'small' will also return true
or try with === will strictly match the values
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;
}

Answer 5

I think you have to change only final_check() function
function final_check() {
if(validate_name($_POST["first_name"])){
return true;
}else{
if (validate_name($_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;
}
}
}