Why a function checking if a string is empty always returns true? [closed]

I have a function isNotEmpty which returns true if the string is not empty and false if the string is empty. I've found out that it is not working if I pass an empty string through it.

function isNotEmpty($input) 
{
    $strTemp = $input;
    $strTemp = trim($strTemp);

    if(strTemp != '') //Also tried this "if(strlen($strTemp) > 0)"
    {
         return true;
    }

    return false;
}

The validation of the string using isNotEmpty is done:

if(isNotEmpty($userinput['phoneNumber']))
{
    //validate the phone number
}
else
{
    echo "Phone number not entered<br/>";
}

If the string is empty the else doesn't execute, I don't understand why, can someone please shed some light on this please.

Solution 1:

Simple problem actually. Change:

if (strTemp != '')

if ($strTemp != '')

Arguably you may also want to change it to:

if ($strTemp !== '')

since != '' will return true if you pass is numeric 0 and a few other cases due to PHP's automatic type conversion.

You should not use the built-in empty() function for this; see comments and the PHP type comparison tables.

Solution 2:

I always use a regular expression for checking for an empty string, dating back to CGI/Perl days, and also with Javascript, so why not with PHP as well, e.g. (albeit untested)

return preg_match('/\S/', $input);

Where \S represents any non-whitespace character

Solution 3:

PHP have a built in function called empty() the test is done by typing if(empty($string)){...} Reference php.net : php empty

Solution 4:

In your if clause in the function, you're referring to a variable strTemp that doesn't exist. $strTemp does exist, though.

But PHP already has an empty() function available; why make your own?

if (empty($str))
    /* String is empty */
else
    /* Not empty */

From php.net:

Return Values

Returns FALSE if var has a non-empty and non-zero value.

The following things are considered to be empty:
* "" (an empty string)
* 0 (0 as an integer)
* "0" (0 as a string)
* NULL
* FALSE
* array() (an empty array)
* var $var; (a variable declared, but without a value in a class)

http://www.php.net/empty

Solution 5:

PHP evaluates an empty string to false, so you can simply use:

if (trim($userinput['phoneNumber'])) {
  // validate the phone number
} else {
  echo "Phone number not entered<br/>";
}