Do:

$x = 0.5;
printf("%.2f", $x);

Get:

0.50

Explanation:

printf() and sprintf() can print/return a formatted string. There are plenty of format parameters available. Here, I used %.2f. Let's take that apart:

• % denotes a placeholder that will be replaced with $x
• . denotes a precision specifier
• 2 belongs to the precision specifier - the number of digits after the decimal point
• f is the type specifier, here float as that's what we're passing in

Alternatively:

Use number_format():

echo number_format($x, 2);

Here, 2 denotes the number of decimal digits you want in the output. You don't actually need to supply a third and fourth parameter, as their defaults are exactly what you want.

Use number_format() function

echo number_format($x,  2, '.', '');

Use number_format Function

<?php
print number_format('0.5',2,'.','');

// 0.50
?>

http://php.net/manual/en/function.number-format.php