For most of us in the US, we don't want to see a "USD" for our currency symbol, so '%i' doesn't cut it.  Here's what I used that worked to get what most  people expect to see for a number format.

$number = 123.4
setlocale(LC_MONETARY, 'en_US.UTF-8');
money_format('%.2n', $number);

output:
$123.40

That gives me a dollar sign at the beginning, and 2 digits at the end.

This is a some function posted before, however various bugs were corrected.

Thank you to Stuart Roe by reporting the bug on printing signals.

<?php
/*
That it is an implementation of the function money_format for the
platforms that do not it bear.  

The function accepts to same string of format accepts for the
original function of the PHP.  

(Sorry. my writing in English is very bad)  

The function is tested using PHP 5.1.4 in Windows XP
and Apache WebServer.
*/
function money_format($format, $number)
{
    $regex  = '/%((?:[\^!\-]|\+|\(|\=.)*)([0-9]+)?'.
              '(?:#([0-9]+))?(?:\.([0-9]+))?([in%])/';
    if (setlocale(LC_MONETARY, 0) == 'C') {
        setlocale(LC_MONETARY, '');
    }
    $locale = localeconv();
    preg_match_all($regex, $format, $matches, PREG_SET_ORDER);
    foreach ($matches as $fmatch) {
        $value = floatval($number);
        $flags = array(
            'fillchar'  => preg_match('/\=(.)/', $fmatch[1], $match) ?
                           $match[1] : ' ',
            'nogroup'   => preg_match('/\^/', $fmatch[1]) > 0,
            'usesignal' => preg_match('/\+|\(/', $fmatch[1], $match) ?
                           $match[0] : '+',
            'nosimbol'  => preg_match('/\!/', $fmatch[1]) > 0,
            'isleft'    => preg_match('/\-/', $fmatch[1]) > 0
        );
        $width      = trim($fmatch[2]) ? (int)$fmatch[2] : 0;
        $left       = trim($fmatch[3]) ? (int)$fmatch[3] : 0;
        $right      = trim($fmatch[4]) ? (int)$fmatch[4] : $locale['int_frac_digits'];
        $conversion = $fmatch[5];

        $positive = true;
        if ($value < 0) {
            $positive = false;
            $value  *= -1;
        }
        $letter = $positive ? 'p' : 'n';

        $prefix = $suffix = $cprefix = $csuffix = $signal = '';

        $signal = $positive ? $locale['positive_sign'] : $locale['negative_sign'];
        switch (true) {
            case $locale["{$letter}_sign_posn"] == 1 && $flags['usesignal'] == '+':
                $prefix = $signal;
                break;
            case $locale["{$letter}_sign_posn"] == 2 && $flags['usesignal'] == '+':
                $suffix = $signal;
                break;
            case $locale["{$letter}_sign_posn"] == 3 && $flags['usesignal'] == '+':
                $cprefix = $signal;
                break;
            case $locale["{$letter}_sign_posn"] == 4 && $flags['usesignal'] == '+':
                $csuffix = $signal;
                break;
            case $flags['usesignal'] == '(':
            case $locale["{$letter}_sign_posn"] == 0:
                $prefix = '(';
                $suffix = ')';
                break;
        }
        if (!$flags['nosimbol']) {
            $currency = $cprefix .
                        ($conversion == 'i' ? $locale['int_curr_symbol'] : $locale['currency_symbol']) .
                        $csuffix;
        } else {
            $currency = '';
        }
        $space  = $locale["{$letter}_sep_by_space"] ? ' ' : '';

        $value = number_format($value, $right, $locale['mon_decimal_point'],
                 $flags['nogroup'] ? '' : $locale['mon_thousands_sep']);
        $value = @explode($locale['mon_decimal_point'], $value);

        $n = strlen($prefix) + strlen($currency) + strlen($value[0]);
        if ($left > 0 && $left > $n) {
            $value[0] = str_repeat($flags['fillchar'], $left - $n) . $value[0];
        }
        $value = implode($locale['mon_decimal_point'], $value);
        if ($locale["{$letter}_cs_precedes"]) {
            $value = $prefix . $currency . $space . $value . $suffix;
        } else {
            $value = $prefix . $value . $space . $currency . $suffix;
        }
        if ($width > 0) {
            $value = str_pad($value, $width, $flags['fillchar'], $flags['isleft'] ?
                     STR_PAD_RIGHT : STR_PAD_LEFT);
        }

        $format = str_replace($fmatch[0], $value, $format);
    }
    return $format;
}

?>

In Rafael M. Salvioni function localeconv(); returns an invalid array in my Windows XP SP3 running PHP 5.4.13 so to prevent the Warning Message: implode(): Invalid arguments passed i just add the $locale manually. For other languages just fill the array with the correct settings.

<?

       $locale = array(
        'decimal_point'        => '.',
        'thousands_sep'        => '',
        'int_curr_symbol'    => 'EUR',
        'currency_symbol'    => '€',
        'mon_decimal_point'    => ',',
        'mon_thousands_sep'    => '.',
        'positive_sign'        => '',
        'negative_sign'     => '-',
        'int_frac_digits'    => 2,
        'frac_digits'        => 2,
        'p_cs_precedes'        => 0,
        'p_sep_by_space'    => 1,
        'p_sign_posn'        => 1,
        'n_sign_posn'        => 1,
        'grouping'            => array(),
        'mon_grouping'        => array(0 => 3, 1 => 3)
        
    );
?>

If money_format doesn't seem to be working properly, make sure you are defining a valid locale.  For example, on Debian, 'en_US' is not a valid locale - you need 'en_US.UTF-8' or 'en_US.ISO-8559-1'.

This was frustrating me for a while.  Debian has a list of valid locales at /usr/share/i18n/SUPPORTED; find yours there if it's not working properly.

To drop zero value decimals, use the following:
<?php
    /*
        Same as php number_format(), but if ends in .0, .00, .000, etc... , drops the decimals altogether
        Returns string type, rounded number - same as php number_format()):
        Examples:
            number_format_drop_zero_decimals(54.378, 2) ==> '54.38'
            number_format_drop_zero_decimals(54.00, 2) ==> '54'
     */
    function number_format_drop_zero_decimals($n, $n_decimals)
    {
        return ((floor($n) == round($n, $n_decimals)) ? number_format($n) : number_format($n, $n_decimals));
    }
?>
Results:
number_format_drop_zero_decimals(54.377, 2) ==> 54.38
number_format_drop_zero_decimals('54.377', 2) ==> 54.38
number_format_drop_zero_decimals(54.377, 3) ==> 54.377
number_format_drop_zero_decimals(54.007, 2) ==> 54.01
number_format_drop_zero_decimals(54.000, 2) ==> 54
number_format_drop_zero_decimals(54.00, 2) ==> 54
number_format_drop_zero_decimals(54.0, 2) ==> 54
number_format_drop_zero_decimals(54.1, 2) ==> 54.10
number_format_drop_zero_decimals(54., 2) ==> 54
number_format_drop_zero_decimals(54, 2) ==> 54
number_format_drop_zero_decimals(54, 3) ==> 54
number_format_drop_zero_decimals(54 + .13, 2) ==> 54.13
number_format_drop_zero_decimals(54 + .00, 2) ==> 54
number_format_drop_zero_decimals(54.0007, 4) ==> 54.0007
number_format_drop_zero_decimals(54.0007, 3) ==> 54.001
number_format_drop_zero_decimals(54.00007, 3) ==> 54  //  take notice

We found that after switching from Ubuntu 10.04 php -v 5.3.2, to Ubuntu 12.04 php -v 5.3.10 this no longer worked:

<?php setlocale(LC_MONETARY, 'en_US'); ?>

Found that using:

<?php setlocale(LC_MONETARY, 'en_US.UTF-8'); ?>

worked find

This function divides integer value by commas. F.e.

<?php
echo formatMoney(1050); # 1,050
echo formatMoney(1321435.4, true); # 1,321,435.40
echo formatMoney(10059240.42941, true); # 10,059,240.43
echo formatMoney(13245); # 13,245

function formatMoney($number, $fractional=false) {
    if ($fractional) {
        $number = sprintf('%.2f', $number);
    }
    while (true) { 
        $replaced = preg_replace('/(-?\d+)(\d\d\d)/', '$1,$2', $number);
        if ($replaced != $number) {
            $number = $replaced;
        } else {
            break;
        }
    }
    return $number;
}
?>

Improvement to Rafael M. Salvioni's solution for money_format on Windows: when no currency symbol is selected, in the formatting, the minus sign was also lost when the locale puts it in position 3 or 4. Changed $currency = '';  to: $currency = $cprefix .$csuffix;

function money_format($format, $number) {
        $regex = '/%((?:[\^!\-]|\+|\(|\=.)*)([0-9]+)?' .
                '(?:#([0-9]+))?(?:\.([0-9]+))?([in%])/';
        if (setlocale(LC_MONETARY, 0) == 'C') {
            setlocale(LC_MONETARY, '');
        }
        $locale = localeconv();
        preg_match_all($regex, $format, $matches, PREG_SET_ORDER);
        foreach ($matches as $fmatch) {
            $value = floatval($number);
            $flags = array(
                'fillchar' => preg_match('/\=(.)/', $fmatch[1], $match) ?
                        $match[1] : ' ',
                'nogroup' => preg_match('/\^/', $fmatch[1]) > 0,
                'usesignal' => preg_match('/\+|\(/', $fmatch[1], $match) ?
                        $match[0] : '+',
                'nosimbol' => preg_match('/\!/', $fmatch[1]) > 0,
                'isleft' => preg_match('/\-/', $fmatch[1]) > 0
            );
            $width = trim($fmatch[2]) ? (int) $fmatch[2] : 0;
            $left = trim($fmatch[3]) ? (int) $fmatch[3] : 0;
            $right = trim($fmatch[4]) ? (int) $fmatch[4] : $locale['int_frac_digits'];
            $conversion = $fmatch[5];

            $positive = true;
            if ($value < 0) {
                $positive = false;
                $value *= -1;
            }
            $letter = $positive ? 'p' : 'n';

            $prefix = $suffix = $cprefix = $csuffix = $signal = '';

            $signal = $positive ? $locale['positive_sign'] : $locale['negative_sign'];
            switch (true) {
                case $locale["{$letter}_sign_posn"] == 1 && $flags['usesignal'] == '+':
                    $prefix = $signal;
                    break;
                case $locale["{$letter}_sign_posn"] == 2 && $flags['usesignal'] == '+':
                    $suffix = $signal;
                    break;
                case $locale["{$letter}_sign_posn"] == 3 && $flags['usesignal'] == '+':
                    $cprefix = $signal;
                    break;
                case $locale["{$letter}_sign_posn"] == 4 && $flags['usesignal'] == '+':
                    $csuffix = $signal;
                    break;
                case $flags['usesignal'] == '(':
                case $locale["{$letter}_sign_posn"] == 0:
                    $prefix = '(';
                    $suffix = ')';
                    break;
            }
            if (!$flags['nosimbol']) {
                $currency = $cprefix .
                        ($conversion == 'i' ? $locale['int_curr_symbol'] : $locale['currency_symbol']) .
                        $csuffix;
            } else {
                $currency = $cprefix .$csuffix;
            }
            $space = $locale["{$letter}_sep_by_space"] ? ' ' : '';

            $value = number_format($value, $right, $locale['mon_decimal_point'], $flags['nogroup'] ? '' : $locale['mon_thousands_sep']);
            $value = @explode($locale['mon_decimal_point'], $value);

            $n = strlen($prefix) + strlen($currency) + strlen($value[0]);
            if ($left > 0 && $left > $n) {
                $value[0] = str_repeat($flags['fillchar'], $left - $n) . $value[0];
            }
            $value = implode($locale['mon_decimal_point'], $value);
            if ($locale["{$letter}_cs_precedes"]) {
                $value = $prefix . $currency . $space . $value . $suffix;
            } else {
                $value = $prefix . $value . $space . $currency . $suffix;
            }
            if ($width > 0) {
                $value = str_pad($value, $width, $flags['fillchar'], $flags['isleft'] ?
                                STR_PAD_RIGHT : STR_PAD_LEFT);
            }

            $format = str_replace($fmatch[0], $value, $format);
        }
        return $format;
    }

Double check that money_format() is defined on any version of PHP you plan your code to run on.  You might be surprised.

For example, it worked on my Linux box where I code, but not on  servers running  BSD 4.11 variants. (This is presumably because strfmon  is not defined - see note at the top of teis page). It's not just a windows/unix issue.

Rafael M. Salvioni's code has a small bug in it when the value is positive and the format provided contains a ( flag.  The value should only be surrounded in parenthesis when the value is negative.  This should fix it:

<?php
    if (!function_exists('money_format'))
    {
        function money_format($format, $number)
        {
            $regex  = '/%((?:[\^!\-]|\+|\(|\=.)*)([0-9]+)?'.
                    '(?:#([0-9]+))?(?:\.([0-9]+))?([in%])/';
            if (setlocale(LC_MONETARY, 0) == 'C') {
                setlocale(LC_MONETARY, '');
            }
            $locale = localeconv();
            preg_match_all($regex, $format, $matches, PREG_SET_ORDER);
            foreach ($matches as $fmatch) {
                $value = floatval($number);
                $flags = array(
                    'fillchar'  => preg_match('/\=(.)/', $fmatch[1], $match) ?
                                $match[1] : ' ',
                    'nogroup'   => preg_match('/\^/', $fmatch[1]) > 0,
                    'usesignal' => preg_match('/\+|\(/', $fmatch[1], $match) ?
                                $match[0] : '+',
                    'nosimbol'  => preg_match('/\!/', $fmatch[1]) > 0,
                    'isleft'    => preg_match('/\-/', $fmatch[1]) > 0
                );
                $width      = trim($fmatch[2]) ? (int)$fmatch[2] : 0;
                $left       = trim($fmatch[3]) ? (int)$fmatch[3] : 0;
                $right      = trim($fmatch[4]) ? (int)$fmatch[4] : $locale['int_frac_digits'];
                $conversion = $fmatch[5];
        
                $positive = true;
                if ($value < 0) {
                    $positive = false;
                    $value  *= -1;
                }
                $letter = $positive ? 'p' : 'n';
        
                $prefix = $suffix = $cprefix = $csuffix = $signal = '';
        
                $signal = $positive ? $locale['positive_sign'] : $locale['negative_sign'];
                switch (true) {
                    case $locale["{$letter}_sign_posn"] == 1 && $flags['usesignal'] == '+':
                        $prefix = $signal;
                        break;
                    case $locale["{$letter}_sign_posn"] == 2 && $flags['usesignal'] == '+':
                        $suffix = $signal;
                        break;
                    case $locale["{$letter}_sign_posn"] == 3 && $flags['usesignal'] == '+':
                        $cprefix = $signal;
                        break;
                    case $locale["{$letter}_sign_posn"] == 4 && $flags['usesignal'] == '+':
                        $csuffix = $signal;
                        break;
                    case $flags['usesignal'] == '(' && !$positive:
                    case $locale["{$letter}_sign_posn"] == 0:
                        $prefix = '(';
                        $suffix = ')';
                        break;
                }
                if (!$flags['nosimbol']) {
                    $currency = $cprefix .
                                ($conversion == 'i' ? $locale['int_curr_symbol'] : $locale['currency_symbol']) .
                                $csuffix;
                } else {
                    $currency = '';
                }
                $space  = $locale["{$letter}_sep_by_space"] ? ' ' : '';
        
                $value = number_format($value, $right, $locale['mon_decimal_point'],
                        $flags['nogroup'] ? '' : $locale['mon_thousands_sep']);
                $value = @explode($locale['mon_decimal_point'], $value);
        
                $n = strlen($prefix) + strlen($currency) + strlen($value[0]);
                if ($left > 0 && $left > $n) {
                    $value[0] = str_repeat($flags['fillchar'], $left - $n) . $value[0];
                }
                $value = implode($locale['mon_decimal_point'], $value);
                if ($locale["{$letter}_cs_precedes"]) {
                    $value = $prefix . $currency . $space . $value . $suffix;
                } else {
                    $value = $prefix . $value . $space . $currency . $suffix;
                }
                if ($width > 0) {
                    $value = str_pad($value, $width, $flags['fillchar'], $flags['isleft'] ?
                            STR_PAD_RIGHT : STR_PAD_LEFT);
                }
        
                $format = str_replace($fmatch[0], $value, $format);
            }
            return $format;
        }    
    }
?>

Consider formatting currency for some South Asian countries that use ##,##,###.## money format.
The following code generates something like Rs. 4,54,234.00 and so on.

<?php
function convertcash($num, $currency){
    if(strlen($num)>3){
            $lastthree = substr($num, strlen($num)-3, strlen($num));
            $restunits = substr($num, 0, strlen($num)-3); // extracts the last three digits
            $restunits = (strlen($restunits)%2 == 1)?"0".$restunits:$restunits; // explodes the remaining digits in 2's formats, adds a zero in the beginning to maintain the 2's grouping.

            $expunit = str_split($restunits, 2);
            for($i=0; $i<sizeof($expunit); $i++){
                $explrestunits .= (int)$expunit[$i].","; // creates each of the 2's group and adds a comma to the end
            }    

            $thecash = $explrestunits.$lastthree;
    } else {
           $thecash = $convertnum;
    }
    
    return $currency.$thecash.".00"; // writes the final format where $currency is the currency symbol.
}
?>

now call the function as  convertcash($row['price'], 'Rs '); // that's the price from the database I called using an Indian Rupees prefix where the price has to be a plain number format, say something like 454234.

If you get "EUR" instead of the euro symbol, set the locale to utf8 charset like this:

<?php
setlocale(LC_MONETARY, 'de_DE.utf8');
echo money_format('%+n', 1234.56);
?>

Hi,

For South Asian Currencies, this function could be a handy one.

It will handle negative as well as float(Paise).

<?php
function my_money_format($number)
{
    if(strstr($number,"-"))
    {
        $number = str_replace("-","",$number);
        $negative = "-";
    }
    
    $split_number = @explode(".",$number);
    
    $rupee = $split_number[0];
    $paise = @$split_number[1];
    
    if(@strlen($rupee)>3)
    {
        $hundreds = substr($rupee,strlen($rupee)-3);
        $thousands_in_reverse = strrev(substr($rupee,0,strlen($rupee)-3));
        for($i=0; $i<(strlen($thousands_in_reverse)); $i=$i+2)
        {
            $thousands .= $thousands_in_reverse[$i].$thousands_in_reverse[$i+1].",";
        }
        $thousands = strrev(trim($thousands,","));
        $formatted_rupee = $thousands.",".$hundreds;
        
    }
    else
    {
        $formatted_rupee = $rupee;
    }
    
    if((int)$paise>0)
    {
        $formatted_paise = ".".substr($paise,0,2);
    }
    
    return $negative.$formatted_rupee.$formatted_paise;

}
?>

Thanks,

This is a handy little bit of code I just wrote, as I was not able to find anything else suitable for my situation.
This will handle monetary values that are passed to the script by a user, to reformat any comma use so that it is not broken when it passes through an input validation system that checks for a float.

It is not foolproof, but will handle the common input as most users would input it, such as 1,234,567 (outputs 1234567) or 1,234.00 (outputs 1234.00), even handles 12,34 (outputs 12.34), I expect it would work with negative numbers, but have not tested it, as it is not used for that in my situation.

This worked when other options such as money_format() were not suitable or possible.

<?php
///////////////
// BEGIN CODE convert all price amounts into well formatted values
function converttonum($convertnum,$fieldinput){
        $bits = explode(",",$convertnum); // split input value up to allow checking
        
        $first = strlen($bits[0]); // gets part before first comma (thousands/millions)
        $last = strlen($bits[1]); // gets part after first comma (thousands (or decimals if incorrectly used by user)
        
        if ($last <3){ // checks for comma being used as decimal place
            $convertnum = str_replace(",",".",$convertnum);
        }
        else{ // assume comma is a thousands seperator, so remove it
            $convertnum = str_replace(",","",$convertnum);
        }
        
        $_POST[$fieldinput] = $convertnum; // redefine the vlaue of the variable, to be the new corrected one
}

@converttonum($_POST[inputone],"inputone");
@converttonum($_POST[inputtwo],"inputtwo");
@converttonum($_POST[inputthree],"inputthree");
// END CODE
//////////////

?>

This is suitable for the English usage, it may need tweaking to work with other types.

Be aware, since PHP 7.3 this method is deprecated and from PHP 7.4 this launch a deprecated error, so, setup your PHP web server to untrack E_DEPRECATED error reporting.