[php] How to check if the input variable is integer?

[michalchojno]

I have a variable submitted throu html form, input tag. I'd like to check if this variable is integer. I used is_numeric() function, but I get an error message when nothing is input in the window.

 

Will is_int() function work better?

 

There is also ereg() function, but I can't figure out how it really works? What's this: [0-9]{4})-([0-9]{1,2} stuff??? What's the right syntax and logic?

Example:

ereg("^[1-9][0-9]*$", $_POST['variable'])

 

How can I make it that when nothing is input, I won't get an error and it will be the same as 0 value?

[ignace]

is_integer() regex is overkill.

[michalchojno]

Not really what I meant. Here is the code I have:

if (!ereg("^[1-9][0-9]*$",($_POST[$val]))) {

echo "Error.";

die();

}

When the input field is empty, I get error. How to make it 0 if empty?

 

EDIT: I changed it to the following and it seems to work.

if (!ereg("^[1-9][0-9]*$",($_POST[$val])) && $_POST[$val] != 0) {

echo "Error.";

die();

}

[michalchojno]

Still could someone please explain how ereg() works? The syntax seems weired. Example: ereg("^[1-9][0-9]*$",($_POST[$val])). Why "^" at the start? Why [1-9[0-9]? Why "*$"?

[flyhoney]

http://us2.php.net/manual/en/function.ctype-digit.php might help you in this case.  Much easier than regex.

 

<?php
$strings = array('1820.20', '10002', 'wsl!12');
foreach ($strings as $testcase) {
    if (ctype_digit($testcase)) {
        echo "The string $testcase consists of all digits.\n";
    } else {
        echo "The string $testcase does not consist of all digits.\n";
    }
}
?>

The above example will output:

The string 1820.20 does not consist of all digits.
The string 10002 consists of all digits.
The string wsl!12 does not consist of all digits.

[Daniel0]

Still could someone please explain how ereg() works? The syntax seems weired. Example: ereg("^[1-9][0-9]*$",($_POST[$val])). Why "^" at the start? Why [1-9[0-9]? Why "*$"?

 

The regular expressions says:

 

Start of string (^) followed by a character in the range 1-9 ([1-9]) followed by a character in the range 0-9 zero or more times ([0-9]*) followed by end of string ($).

 

Google: "regex"

And see: http://www.phpfreaks.com/tutorial/regular-expressions-part1---basic-syntax

 

By the way, preg is faster than ereg.

[flyhoney]

^[1-9][0-9]*$

 

That is a regular expression.  The "^" represents the beginning of the string and "$" represents the end.  These are necessary because without them, the above expression would also match strings like: "blah blag 83983 roflcopter".

 

[1-9] matches a number 1-9 obviously.

 

[0-9]* matches any number of numbers 0-9.

 

So it looks like this expression is meant to match any number equal to or greater than 1.

[michalchojno]

Thanks. This is really awesome help with great examples.

 

What actually happens if nothing is input in the input window? The input variable seems empty. And in such case, my code seems to still display an error no matter how I check it for integer.

[9three]

You need to do if conditions.

 

if (empty($userInt) || !ctype_digit($userInt)) {
  echo 'A number must be inputted before proceeding';
else {
  //do whatever you want
}

[flyhoney]

Just make sure it isn't empty first!

 

$foo = $_POST['foo'];

if ($foo and ctype_digit($foo) !== FALSE)
{
    // It's a digit!
}

[michalchojno]

Geeez, frustrating, It doesn't work...

 

If the field is empty (a person didn't put anything in), I'd like to allow it and treat it as 0. Instead I keep getting "Error".

 

Here is what I typed, which doesn't seem to fix it.

if (empty($val)) {$val = 0;}

if (!ctype_digit($val)) {

echo "Error";

die();

}

[Coreye]

Try this:

<?php
if (empty($val)) {
	$val = "0";
}
if (!ctype_digit($val)) {
	die("Error");
}
?>

[jcrew]

You could have done:

 

$int = intval($_POST[whatever]);
if(is_numeric($int)){

}// .. etc.

[michalchojno]

No, no... ctype_digit() seems to generate error when the value is 0. I used ereg("^[0-9[0-9]*$", $val) and if empty($val) {$val = 0} and it works.

[Daniel0]

Then try this:

 

if (preg_match('#^(?:0|-?[1-9]\d*)$#', $val)) {

}