[PHP知识库]PHP 将字符串映射成数字，同时可以将数字映射成字符串

字符串转成int，int反解可反推得到原有字符串

比如：str = "leyangjun"? ?---> 得到：? 123456789

? ? ? ? ? ?123456789? ----> 反解得到：“leyangjun”

代码如下

/**
 * 字符串转成int，int可反解字符串
 * User: leyangjun
 * Date: 2020/3/23
 * Time: 下午3:29
 */

namespace leyangjun\lib;

<?php

class base62Parse {

    private $string = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    private $encodeBlockSize = 7;
    private $decodeBlockSize = 4;
    /**
     * 将mid转换成62进制字符串
     *
     * @param	string	$mid
     * @return	string
     */
    public function encode($mid) {
        $str = "";
        $midlen = strlen($mid);
        $segments = ceil($midlen / $this->encodeBlockSize);
        $start = $midlen;
        for($i=1; $i<$segments; $i+=1) {
            $start -= $this->encodeBlockSize;
            $seg = substr($mid, $start, $this->encodeBlockSize);
            $seg = $this->encodeSegment( $seg );
            $str = str_pad($seg, $this->decodeBlockSize, '0', STR_PAD_LEFT) . $str;
        }
        $str = $this->encodeSegment( substr($mid, 0, $start) ) . $str;
        return $str;
    }

    /**
     * 将62进制字符串转成10进制mid
     *
     * @param	string	$str
     * @return	string
     */
    public function decode($str, $compat=false ,$for_mid=true) {
        $mid = "";
        $strlen = strlen($str);
        $segments = ceil($strlen / $this->decodeBlockSize);
        $start = $strlen;
        for($i=1; $i<$segments; $i+=1) {
            $start -= $this->decodeBlockSize;
            $seg = substr($str, $start, $this->decodeBlockSize);
            $seg = $this->decodeSegment( $seg );
            $mid = str_pad($seg, $this->encodeBlockSize, '0', STR_PAD_LEFT) . $mid;
        }
        $mid = $this->decodeSegment( substr($str, 0, $start)) . $mid;
        if($compat && !in_array(substr($mid, 0, 3), array('109', '110', '201', '211', '221', '231', '241'))) {
            $mid = $this->decodeSegment(substr($str, 0, 4)).$this->decodeSegment(substr($str, 4));
        }
        if($for_mid){
            if(substr($mid, 0, 1)=='1' && substr($mid, 7, 1)=='0') {
                $mid = substr($mid, 0, 7).substr($mid, 8);
            }
        }
        return $mid;
    }


    /**
     * 将10进制转换成62进制
     *
     * @param	string	$str	10进制字符串
     * @return	string
     */
    private function encodeSegment($str) {
        $out = '';
        while($str > 0){
            $idx = $str % 62;
            $out = substr($this->string, $idx, 1) . $out;
            $str = floor($str / 62);
        }
        return $out;
    }

    /**
     * 将62进制转换成10进制
     *
     * @param	string	$str	62进制字符串
     * @return	string
     */
    private function decodeSegment($str) {
        $out = 0;
        $base = 1;
        for($t=strlen($str) - 1;$t>=0;$t-=1) {
            $out = $out + $base * strpos($this->string, substr($str, $t, 1));
            $base *= 62;
        }
        return $out . "";
    }

}


$v = new base62Parse();

//print_r($v->encode(12345));
print_r($v->decode('3d7'));