I need to be able to see if a form input in PHP is numeric. If it is not numeric, the website should redirect. I have tried is_numeric() but it does not seem to work.
Code examples will be nice.
I am developing a shopping cart that accepts an integer value for the quantity. I am trying this:
if(!is_numeric($quantity)){
//redirect($data['referurl']."/badinput");
echo "is not numeric";
}
if(!is_numeric($quantity == 0)){
//redirect($data['referurl']."/badinput");
echo "is not numeric";
What you have here are two nested conditions. Let's say $quantity is 1.
The first condition evaluates 1 == 0 and returns FALSE. The second condition checks if FALSE is numeric and returns FALSE because FALSE is not numeric.
just write:
if (!is_numeric($quantity))
{
echo 'is not numeric';
}
You should probably explain what you mean by "numeric" - integral, floating point, exponential notation etc? is_numeric() will accept all of these.
If you want to check that a string contains nothing other than digits, then you could use a regular expression, e.g.
/^\d+$/
If you're going to use the actual value as if it were an integer, you'll probably want to pass it through intval() anyway, which will return 0 if the value cannot be parsed - if 0 is a valid value, then you'll probably have to handle that in some way, maybe by constraining the lower range of the value.
It might also be wise to do some client side validation of the input using JavaScript.
The round-trip to the server and back is a long one for what might amount to a typo, and you'll reduce server overhead by making the client browser do a bit of the quality assurance beforehand.
Check is_int and is_numeric. There are examples in each of the links. If you need more help, I would post the data you are having problems with and a code sample.
EDIT:
$quantity == 0
will always be numeric, since it will return a boolean value (1 or 0). The correct thing to do it:
if ( is_numeric( $quantity ) ) {
...
}
or
if ( is_int( $quantity ) ) {
...
}
Another alternative is ctype_digit. From the docs:
Checks if all of the characters in the provided string, text, are numerical. Returns TRUE if every character in the string text is a decimal digit, FALSE otherwise.
<?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.
<?php
$numeric_string = '42';
$integer = 42;
ctype_digit($numeric_string); // true
ctype_digit($integer); // false (ASCII 42 is the * character)
is_numeric($numeric_string); // true
is_numeric($integer); // true
?>
tharkun has the best answer so far. If you're asking a question like this, it's my guess that you don't really want to start messing around with reg-exp's just yet.
Re-think your logic. Why do you want to check to see if $quantity==0 is a numeric result? If you're trying to avoid errors b/c you think it's possible for quantity to not have an assigned value, you're checking a little late. This is a very common (and nefarious) security hole in your application -- if $quantity has a value derived at all from user input, please make sure to sanitize the input before it reaches this point in execution. As a smaller part of the issue, you will not need to assign a default value, because you sanitized your input previously (and that sanitization is where you'd deal with a 'no input' situation).
Good luck!
Use regular expressions: /^\d+$/ should solve the problem
Try this:
$numeric = "1"; //true default
$string = trim($_GET['string']);
$chkarray = array("0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", ",", ".");
for ($i=0; $i < strlen($string); $i++) {
if (!in_array(substr($string, $i, 1), $chkarray)) {
$numeric = "0";
break;
}
}
