How to find if a number is odd or even?
In PHP I learn to use the MOD (%) operator. see below for an example: $i = 10;

if ($i % 2) {
echo "$i is odd";
} else {
echo "$i is even";
}


You can also use the PHP “&” operator that will give you better performance
You can use the PHP code like so:

$i = 10;
if ( $i&1 )
{
echo "$i is odd";
}
else
{
echo "$i is even";
}

Answer:
Just check the number value during a loop in php to see if it’s less then 10.
Php code is below:
If so then add the leading zero to your string.

<?
for ($num = 1; $num <= 31; $num++) {
if($num<10)
$day = "0$num"; // add the zero
else
$day = "$num"; // don't add the zero
echo "<p>$day</p>";
?>

Question: How to validate number values to and block all letters and symbol in a form.

Answer: You can check the value or convert the value to an integer (number).

1) Check a value using is_int() to finds whether the given variable is an integer

<?
if(is_int($variable))
echo "Pass test";
else
echo "Please use only numbers";
?>

2) Note: To test if a variable is a number or a numeric string (such as form input, which is always a string), you must use is_numeric().

<?
if(is_numeric($variable))
echo "Pass test";
else
echo "Please use only numbers";
?>

3) Convert the value to an integer (number) using settype.

<?php
$foo = "5bar"; // string
$bar = true; // boolean

settype($foo, “integer”); // $foo is now 5 (integer)
settype($bar, “string”); // $bar is now “1″ (string)
?>

or you can use int to do the trick.


<?
$int=593; // $int is a integer
$int.=""; // $int is now a string
?>


Round a number up or down or Round off a floating decimal point number using PHP’s functions round().

Example. round();
echo round(3.4); // 3
echo round(3.5); // 4
echo round(3.6); // 4
echo round(3.6, 0); // 4
echo round(1.95583, 2); // 1.96
echo round(1241757, -3); // 1242000
echo round(5.045, 2); // 5.05
echo round(5.055, 2); // 5.06
?>

Convert to Decimal Point

Example. number_format();
$number = “28″;
$number = number_format($number, 2);
echo $number; // equals “28.00″
?>

For a good book on PHP, check out Beginning PHP4