如何将一个非常大的数字压缩成字母数字(在PHP中）

这是我以前为c++应用程序制作的一个。请随意使用。

// $num - the number we want to convert
// $symbols - the chars you want to use e.g. '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
// &$out is a pointer to your $result
function intToBase($num, $symbols, &$out){
    
    // get the radix that we are working with
    $radix = strlen($symbols);
    
    $pos = strlen($out)-1;
    
    if($num==0){
        // if our number is zero then we can just use the first character of our symbols and we are done.
        $out[$pos] = $symbols[0];
    }else{
        // otherwise we have to loop through and rebase the integer one character at a time.
        while ($num > 0) {
            // split off one digit
           $r = $num % $radix;
            // convert it and add it to the char array
            $out[$pos] = $symbols[$r];
            // subtract what we have added to the compressed string
            $num = ($num - $r) / $radix;
            $pos--;
        }
    }
};

简单使用：

$num = 123004954712; //whatever number you want to compress
$result = "";// the result variable we will be writing to
$chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';// the caracters of our custom base.
intToBase($num, $chars, $result);// the call
// now our $result variable will have the rebased string.

为了完成Goran的答案并节省某人的时间，以下是在转换后返回int值的函数：

function baseToInt($base, $symbols, &$out) {
    //get length of the char map, so you can change according to your needs
    $radix = strlen($symbols);
    //split the chars into an array and initialize variables
    $arr = str_split($base,1);
    $i = 0;
    $out = 0;
    //loop through each char assigning values
    //chars to the left are the least significant
    foreach($arr as $char) {
        $pos = strpos($symbols, $char);
        $partialSum = $pos * pow($radix, $i);
        $out += $partialSum;
        $i++;
    }
}

这个电话和戈兰的完全一样：

$number = 123456;
$symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$strBase = "";
intToBase($number, $symbols, $strBase);
$intReturn = 0;
baseToInt($strBase, $symbols , $intReturn);
echo $strBase."<br>"; //e7w
echo $intReturn; //123456

Goran的答案是完全有效的，但多年来PHP变得更加严格，并略微改变了引用的使用，因此要将其更新到今天，我们可以使用：

function intToBase(int $num)
{
    $symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    // get the radix that we are working with
    $radix = strlen($symbols);
    $out   = [];
    if ($num === 0) {
        // if our number is zero then we can just use the first character of our symbols and we are done.
        return $symbols[0];
    }
    // otherwise we have to loop through and rebase the integer one character at a time.
    while ($num > 0) {
        // split off one digit
        $r = $num % $radix;
        // convert it and add it to the char array
        array_unshift($out, $symbols[$r]);
        // subtract what we have added to the compressed string
        $num = (int)floor(($num - $r) / $radix);
    }

    return implode('', $out);
}

此版本将适用于严格类型。

基于上述算法，我使用GMP修复了它，使其也能处理非常长的数字。它的代码更有效，并且共享两种编码/解码方式：

function intToBase(int|string $num)
{
    // sometimes $num is sent using gmt_intval which of type string on very very large numbers                                                                     
    if ( ! is_numeric($num) ) return 0;
    $symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    // get the radix that we are working with
    $radix = strlen($symbols);
    $out   = [];
    if ($num === 0) { 
        // if our number is zero then we can just use the first character of our symbols and we are done.
        return $symbols[0];
    }    
    // otherwise we have to loop through and rebase the integer one character at a time.
    while ($num > 0) { 
        // split off one digit
        $r = (int) gmp_div_r ($num, $radix);  // $num % $radix
        // convert it and add it to the char array
        $out[] = $symbols[$r];
        // subtract what we have added to the compressed string
        $num = gmp_div ( gmp_sub($num, $r), $radix); // ($num-$r) / $radix
    }    
    return implode('', array_reverse($out));
}
function baseToInt($base) {
    $symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    //get length of the char map, so you can change according to your needs
    $radix = strlen($symbols);
    //split the chars into an array and initialize variables
    $arr = str_split($base,1);
    $out = 0;
    //loop through each char assigning values
    //chars to the left are the least significant
    foreach($arr as $char) {
        $pos = strpos($symbols, $char);
        $out = gmp_add ( gmp_mul ($out,$radix), $pos);  //  ($out*radix) + $pos
    }                                                                                                                                                              
    return $out;
}