Why Does PHP Display Small Decimal Numbers in Scientific Notation, and How Can I Prevent It?

PHP's Scientific Notation Conundrum

In PHP, you may encounter an unexpected behavior when handling decimal numbers. As demonstrated in the code snippet below, specifying a number with a decimal point doesn't guarantee that it will be printed in the desired format:

<?PHP
  $var = .000021;
  echo $var;
?>

Surprisingly, the output of this code is "2.1E-5" instead of the expected ".000021". This scientific notation is often undesirable when working with precise numerical values.

The Reason Behind Scientific Notation

PHP internally represents numbers using floating-point arithmetic. When a number has many trailing zeros, PHP defaults to scientific notation to maintain precision and avoid inaccurate rounding. In this case, ".000021" has five trailing zeros, leading to the use of scientific notation.

Overcoming Scientific Notation

To prevent scientific notation, you can use the number_format() function:

print number_format($var, 5);

Here, the "5" argument specifies the number of decimal places to retain. This function will output ".000021" as expected.

Additionally, you can consider using sprintf() to control the output format:

printf("%.5f", $var);

This approach also ensures that the number is printed with five decimal places.

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