Check if number is decimal

Question

I need to check in PHP if user entered a decimal number (US way, with decimal point: X.XXX)

Any reliable way to do this?

Answer 1

   // if numeric 

if (is_numeric($field)) {
        $whole = floor($field);
        $fraction = $field - $whole;

        // if decimal            
        if ($fraction > 0)
            // do sth
        else
        // if integer
            // do sth 
}
else

   // if non-numeric
   // do sth

Answer 2

If all you need to know is whether a decimal point exists in a variable then this will get the job done...

function containsDecimal( $value ) {
    if ( strpos( $value, "." ) !== false ) {
        return true;
    }
    return false;
}

This isn't a very elegant solution but it works with strings and floats.

Make sure to use !== and not != in the strpos test or you will get incorrect results.

Answer 3

This is a more tolerate way to handle this with user input. This regex will match both "100" or "100.1" but doesn't allow for negative numbers.

/^(\d+)(\.\d+)?$/

Answer 4

function is_decimal_value( $a ) {
    $d=0; $i=0;
    $b= str_split(trim($a.""));
    foreach ( $b as $c ) {
        if ( $i==0 && strpos($c,"-") ) continue;
        $i++;
        if ( is_numeric($c) ) continue;
        if ( stripos($c,".") === 0 ) {
            $d++;
            if ( $d > 1 ) return FALSE;
            else continue;
        } else
        return FALSE;
    }
    return TRUE;
}

Known Issues with the above function:

1) Does not support "scientific notation" (1.23E-123), fiscal (leading $ or other) or "Trailing f" (C++ style floats) or "trailing currency" (USD, GBP etc)

2) False positive on string filenames that match a decimal: Please note that for example "10.0" as a filename cannot be distinguished from the decimal, so if you are attempting to detect a type from a string alone, and a filename matches a decimal name and has no path included, it will be impossible to discern.

Answer 5

$lat = '-25.3654';

if(preg_match('/./',$lat)) {
    echo "\nYes its a decimal value\n";
}
else{
    echo 'No its not a decimal value';
}