php strcmp function

Question

I have the following code:

if(strcmp($_POST['password'], $_POST['password-rpt']) == 0) {  
    $password_field = $_POST['password'];  
    echo "Password created" . "<br />";  
} else {  
    echo "blarg! Password mismatch!!!";  
}

I know that like C/C++ strcmp is supposed to return 0 when the two strings are the same but when I test it with an html file, entering two identical strings or two different ones, both cases go to the error case and my output is "blarg! Password mismatch!!!"

Here is the form I used:

<form method="post" action="register.php">
        Name: <input type="text" name = "name" id="name" /><br />
        Password: <input type="password" name ="password" id = "password" /> <br />
        Confirm Password: <input type="password" name="password_rpt" id="password_rpt" /> <br />
        email:    <input type="text" name = "remail" id = "remail" /><br />

        <input type = "submit" name="register" id="register"  value = "Sign Up" />
    </form>

What am I missing?

Update: I changed the condition to if($_POST['password'] == $_POST['password-rpt']). Hasn't helped.

Probably a typo in your form that we can't see. This isn't your actual code since it wouldn't execute with the missing parentheses. — Dan Grossman
– Dan Grossman, Commented Aug 2, 2011 at 15:57

rid · Accepted Answer · 2016-05-12 19:17:15Z

4

You can simply use:

$_POST['password'] === $_POST['password-rpt']

Also, in your form, you used the name password_rpt, while in your code, you refer to password-rpt. You need to change one of them so that the names match.

Take a look at the Strings manual page to learn more about string handling in PHP. I also recommend having a look at the Language Reference for general guidance.

Do keep in mind that PHP is a high level scripting language, and is very different from C++, even if they might look the same. There are things that are very feasible in C++ but not in PHP, and vice versa.

edited May 12, 2016 at 19:17

answered Aug 2, 2011 at 15:57

rid

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4 Comments

Isaac Over a year ago

Thanks. I didn't know that. C++ can't do that and my book didn't mention it.

rid Over a year ago

@Yitzchak, updated answer to reflect changes in the question.

Isaac Over a year ago

yes. I realized that while I was looking over my edits before saving. I am officially an idiot.

Shapi Over a year ago

What if '1e3' == '1000'?

Night Owl · Accepted Answer · 2011-08-02 16:21:19Z

2

For passwords you really want to be using === (identical) as == (equal) will return true even if case does not match...

if( $_POST['password'] === $_POST['password-rpt'] ) {  
    $password_field = $_POST['password'];  
    echo "Password created" . "<br />";  
} else {  
    echo "blarg! Password mismatch!!!";  
}

answered Aug 2, 2011 at 16:21

Night Owl

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3 Comments

Isaac Over a year ago

Thanks for the advice. Where can I read more about php string operations?

Night Owl Over a year ago

I stand corrected on my case comment it was incorrect. I also, however, stand behind on my use of the === operator as things like $pass1 = true, $pass2 = "mypassword", ($pass1 == $pass2) will evaluate to true. Basically because of php's loose and dynamic typing there are a lot of ways that == can yield unwelcome results.

Shapi Over a year ago

+1 for the answer. you should never use the equal operator for strings. correct awenser is the identical operator ===.

Shapi · Accepted Answer · 2016-05-11 15:09:01Z

0

Keep in mind that strcmp() returns:

-1 if str1 is less than str2;
1 if str1 is greater than str2;
0 if they are equal;

Similar to == (equal operator) as in strcmp('1e3', '1000') (return value 0 ), or '1e3'=='1000' (true).

Note, PHP 7 have a similar operator, spaceship operator (<=>) and have the same behaviour than strcmp().

In your case you should use :

if ($_POST['password'] === $_POST['password-rpt'])

answered May 11, 2016 at 15:09

Shapi

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Comments

Tarek Fadel · Accepted Answer · 2011-08-02 15:59:32Z

-1

Why are you using strcmp()? You'd get the desired result if you did

if ($_POST['password'] == $_POST['password-rpt'])

answered Aug 2, 2011 at 15:59

Tarek Fadel

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2 Comments

Mark Biesheuvel Over a year ago

That's because he probably is used to C in which == won't work on strings, since it returns only true if the char pointers are equal.

Shapi Over a year ago

wrong answer. '1e3' == '1000' returns true, and its not the intention

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