Truncate Float Numbers with PHP

How do I truncate a decimal in PHP?

Yes intval

intval(1234.567);
intval(-1234.567);

No Truncate function in PHP - Options?

You can use PHP's floor function along with some decimal shifting like so:

floor(0.7666666667 * 100) / 100;

PHP dropping decimals without rounding up

You need floor() in this way:

$rounded = floor($float*100)/100;

Or you cast to integer:

$rounded = 0.01 * (int)($float*100);

This way it will not be rounding up.

Show a number to two decimal places

You can use number_format():

return number_format((float)$number, 2, '.', '');

Example:

$foo = "105";
echo number_format((float)$foo, 2, '.', '');  // Outputs -> 105.00

This function returns a string.

Can FLOAT types be truncated in MySQL stored functions?

Yes they are incompatible.

FLOAT stores the data in a IEEE-754 binary format which is stored in base 2. A base 10 fraction does not fit exactly. Thus your function gets something near 0.0012345 for the truncation but a FLOAT cannot hold that exact so you get the number required.
See the many answers here and elsewhere especially What Every Computer Scientist Should Know About Floating-Point Arithmetic for what a IEEE format floating point number is represented as.

If you want to have an exact number of decimal places you need to use the DECIMAL type

Delete digits after two decimal points, without rounding the value

TL;DR:

The PHP native function bcdiv seems to do precisely what is required, and properly.

To simply "truncate" a number, bcdiv($var, 1, 2); where 2 is the number of decimals to preserve (and 1 is the denomenator - dividing the number by 1 allows you to simply truncate the original number to the desired decimal places)

Full Answer (for history)

This turns out to be more elusive than one might think.

After this answer was (incorrectly) upvoted quite a bit, it has come to my attention that even sprintf will round.

Rather than delete this answer, I'm turning it into a more robust explanation / discussion of each proposed solution.

number_format - Incorrect. (rounds)
Try using number format:

$var = number_format($var, 2, '.', '');  // Last two parameters are optional
echo $var;
// Outputs 2.50

If you want it to be a number, then simply type-cast to a float:

$var = (float)number_format($var, 2, '.', '');

Note: as has been pointed out in the comments, this does in fact round the number.

sprintf - incorrect. (sprintf also rounds)
If not rounding the number is important, then per the answer below, use sprintf:

$var = sprintf("%01.2f", $var);

floor - not quite! (floor rounds negative numbers)

floor, with some math, will come close to doing what you want:

floor(2.56789 * 100) / 100; // 2.56

Where 100 represents the precision you want. If you wanted it to three digits, then:

floor(2.56789 * 1000) / 1000; // 2.567

However, this has a problem with negative numbers. Negative numbers still get rounded, rather than truncated:

floor(-2.56789 * 100) / 100; // -2.57

"Old" Correct answer: function utilizing floor

So a fully robust solution requires a function:

function truncate_number( $number, $precision = 2) {
    // Zero causes issues, and no need to truncate
    if ( 0 == (int)$number ) {
        return $number;
    }
    // Are we negative?
    $negative = $number / abs($number);
    // Cast the number to a positive to solve rounding
    $number = abs($number);
    // Calculate precision number for dividing / multiplying
    $precision = pow(10, $precision);
    // Run the math, re-applying the negative value to ensure returns correctly negative / positive
    return floor( $number * $precision ) / $precision * $negative;
}

Results from the above function:

echo truncate_number(2.56789, 1); // 2.5
echo truncate_number(2.56789);    // 2.56
echo truncate_number(2.56789, 3); // 2.567

echo truncate_number(-2.56789, 1); // -2.5
echo truncate_number(-2.56789);    // -2.56
echo truncate_number(-2.56789, 3); // -2.567

New Correct Answer

Use the PHP native function bcdiv

echo bcdiv(2.56789, 1, 1);  // 2.5
echo bcdiv(2.56789, 1, 2);  // 2.56
echo bcdiv(2.56789, 1, 3);  // 2.567
echo bcdiv(-2.56789, 1, 1); // -2.5
echo bcdiv(-2.56789, 1, 2); // -2.56
echo bcdiv(-2.56789, 1, 3); // -2.567

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