How to upload pictures and change names in php

How to upload pictures and change their names in php: 1. Rename the uploaded pictures through the GUID method; 2. Use the MD5 method; 3. Use the uniqid method; 4. Use the fast_uuid method, etc.

The operating environment of this article: Windows 7 system, PHP version 7.1, Dell G3 computer

How to upload pictures and change the name in php?

6 examples of methods to rename php uploaded images

1. Applicable scenarios:
cannot be used from the database The returned self-increasing number is used to rename the uploaded image.
This is determined by the process of uploading images or files.
The general image upload process is to first upload the image to the server, rename it, and then insert it into the database.
In other words, the self-increasing ID that is very easy to obtain in the database cannot be used to rename uploaded pictures to avoid duplication of file names.
The method of obtaining the maximum ID plus 1 from the database is used. , increases the number of database connections, and is not suitable for situations with high concurrency and huge data volume;
2. Conventional solution:
1, guid: 32-character hexadecimal number.
Format: The format of the GUID is "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", where each x is a 32-digit hexadecimal number in the range of 0-9 or a-f. For example: 6F9619FF-8B86-D011-B42D-00C04FC964FF is a valid GUID value.
Advantages: Almost no duplication;
Disadvantages: It is still too long for renaming uploaded pictures.
Usage:

The code is as follows:

/*
    com_create_guid()是php5版本支持的功能，对于不支持的版本，可以自己进行定义；
*/
function guid(){
   if (function_exists('com_create_guid')){
       return com_create_guid();
   }else{
       mt_srand((double)microtime()*10000);//optional for php 4.2.0 and up.
       echo(mt_rand());
       $charid = strtoupper(md5(uniqid(rand(), true)));
       $hyphen = chr(45);// "-"
       $uuid = chr(123)// "{"
               .substr($charid, 0, 8).$hyphen
               .substr($charid, 8, 4).$hyphen
               .substr($charid,12, 4).$hyphen
               .substr($charid,16, 4).$hyphen
               .substr($charid,20,12)
               .chr(125);// "}"
       return $uuid;
   }
}

2, MD5:
will output the same 32-character hexadecimal number as guid, the difference is guid It is generated randomly, and md5 needs to be generated based on the input data.
Example:

The code is as follows:

<?php
$str = "Hello";
echo md5($str);
?>

Output

8b1a9953c4611296a827abf8c47804d7

Advantages: The output can be controlled based on the input seed data Numerical values, if the seed data is regular and non-repeating, the data can be protected through md5, which will cause great confusion.
Disadvantages: 32-bit characters are too long; non-duplicate seed data needs to be provided;
Usage: High concurrency, with seconds as the seed data, duplication will still occur.

The code is as follows:

<?php
/*
*结合time()函数使用，以1970年到当前时间的秒数作为种子数。
*/
$str=time();
echo md5($str);
?>

3, uniqid(): returns a 13 or 23-digit string
For our purposes, uniqid() is like md5() The improved version, in particular, we can use differential identifiers as string prefixes, which can reduce the chance of repeated naming.
For extreme situations such as non-high concurrency, it is recommended to use this function, which can already meet general needs.
Details,
Definition: The uniqid() function generates a unique ID based on the current time in microseconds.
Usage: uniqid(prefix,more_entropy)
Description: prefix can add a prefix to the output string. The example is as follows. When the more_entropy parameter is true, a 23-bit string will be output.

The code is as follows:

<?php
var_dump(uniqid());
var_dump(uniqid("a"));
?>

The output result is:

string(13) "51734aa562254" string(14) "a51734aa562257"

Advantages: 13-digit string length is an acceptable file naming length; OK By adding a prefix, the result contains data obfuscation, which can avoid back-referencing the original data.
Disadvantages: Similar to md5, high concurrency, using seconds as the seed data, duplication will still occur.
3. Upgraded version plan:
1, fast_uuid: returns 17 digits
It is a bit like an incomplete customized version of uniqid(), the "seed number start time" that appears in this function "The concept is inspiring.
The default time used in time() and uniqid() is calculated from 1970, and the length is ten digits (1366512439). Using the "seed number starting time" can reduce this value, because we actually need Yes, it is just a value that can grow automatically.
After the starting time is customized, in addition to reducing the length, it can also play a role in confusion.

The code is as follows:

/*
* 参数 suffix_len指定 生成的 ID 值附加多少位随机数，默认值为 3。
* 感谢“Ivan Tan|谭俊青 DrinChing (at) Gmail.com”提供的算法。
* @param int suffix_len
* @return string
*/
function fast_uuid($suffix_len=3){
    //! 计算种子数的开始时间
    $being_timestamp = strtotime('2013-3-21');
    $time = explode(' ', microtime());
    $id = ($time[1] - $being_timestamp) . sprintf('%06u', substr($time[0], 2, 6));
    if ($suffix_len > 0)
    {
        $id .= substr(sprintf('%010u', mt_rand()), 0, $suffix_len);
    }
    return $id;
}

Output,

29832412631099013

2, time() random number:
Random numbers have already appeared in the above example The use is to solve multiple requests that occur in one second. Two functions are provided as follows,

The code is as follows:

<?php
function random($length) {
    $hash = &#39;&#39;;
    $chars = &#39;ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz&#39;;
    $max = strlen($chars) - 1;
    PHP_VERSION < &#39;4.2.0&#39; && mt_srand((double)microtime() * 1000000);
    for($i = 0; $i < $length; $i++) {
        $hash .= $chars[mt_rand(0, $max)];
    }
    return $hash;
}
function random2($length, $numeric = 0) {
    PHP_VERSION < &#39;4.2.0&#39; ? mt_srand((double)microtime() * 1000000) : mt_srand();
    $seed = base_convert(md5(print_r($_SERVER, 1).microtime()), 16, $numeric ? 10 : 35);
    $seed = $numeric ? (str_replace(&#39;0&#39;, &#39;&#39;, $seed).&#39;012340567890&#39;) : ($seed.&#39;zZ&#39;.strtoupper($seed));
    $hash = &#39;&#39;;
    $max = strlen($seed) - 1;
    for($i = 0; $i < $length; $i++) {
        $hash .= $seed[mt_rand(0, $max)];
    }
    return $hash;
}
?>

4. Final solution:
Idea: userid seconds random number. Among them, "userid seconds" is converted from decimal to 64, reducing the number of digits;
Description:
userid: The maximum value of "ZZZZ" in 64 is converted to decimal equal to "16777215", and the maximum value of "ZZZ" is converted to decimal The value is equal to "262143";
Seconds: Set your own time starting point.
$less=time()-strtotime('2012-4-21′); Convert to hexadecimal "1SpRe", 5 digits
$less=time()-strtotime('2013-3-21 ′); Convert to hexadecimal "_jHY"; 4-digit random number
: Use random(3) to generate a 3-digit random number;
Final result:
4-digit userid 4-digit second 3-digit random number =11-digit string. Although the results look similar to uniqid(), the robustness is improved.
5. Algorithm for converting decimal to hexadecimal:
Algorithm 1:

The code is as follows:

const KeyCode = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$';
    /**
     * 将64进制的数字字符串转为10进制的数字字符串
     * @param $m string 64进制的数字字符串
     * @param $len integer 返回字符串长度，如果长度不够用0填充，0为不填充
     * @return string
     * @author 野马
     */
    function hex64to10($m, $len = 0) {
        $m = (string)$m;
        $hex2 = '';
        $Code = KeyCode;
        for($i = 0, $l = strlen($Code); $i < $l; $i++) {
            $KeyCode[] = $Code[$i];
        }
        $KeyCode = array_flip($KeyCode);
        for($i = 0, $l = strlen($m); $i < $l; $i++) {
            $one = $m[$i];
            $hex2 .= str_pad(decbin($KeyCode[$one]), 6, &#39;0&#39;, STR_PAD_LEFT);
        }
        $return = bindec($hex2);
        if($len) {
            $clen = strlen($return);
            if($clen >= $len) {
                return $return;
            }
            else {
                return str_pad($return, $len, &#39;0&#39;, STR_PAD_LEFT);
            }
        }
        return $return;
    }
    /**
     * 将10进制的数字字符串转为64进制的数字字符串
     * @param $m string 10进制的数字字符串
     * @param $len integer 返回字符串长度，如果长度不够用0填充，0为不填充
     * @return string
     * @author 野马
     */
    function hex10to64($m, $len = 0) {
        $KeyCode = KeyCode;
        $hex2 = decbin($m);
        $hex2 = str_rsplit($hex2, 6);
        $hex64 = array();
        foreach($hex2 as $one) {
            $t = bindec($one);
            $hex64[] = $KeyCode[$t];
        }
        $return = preg_replace(&#39;/^0*/&#39;, &#39;&#39;, implode(&#39;&#39;, $hex64));
        if($len) {
            $clen = strlen($return);
            if($clen >= $len) {
                return $return;
            }
            else {
                return str_pad($return, $len, &#39;0&#39;, STR_PAD_LEFT);
            }
        }
        return $return;
    }
    /**
     * 将16进制的数字字符串转为64进制的数字字符串
     * @param $m string 16进制的数字字符串
     * @param $len integer 返回字符串长度，如果长度不够用0填充，0为不填充
     * @return string
     * @author 野马
     */
    function hex16to64($m, $len = 0) {
        $KeyCode = KeyCode;
        $hex2 = array();
        for($i = 0, $j = strlen($m); $i < $j; ++$i) {
            $hex2[] = str_pad(base_convert($m[$i], 16, 2), 4, &#39;0&#39;, STR_PAD_LEFT);
        }
        $hex2 = implode(&#39;&#39;, $hex2);
        $hex2 = str_rsplit($hex2, 6);
        foreach($hex2 as $one) {
            $hex64[] = $KeyCode[bindec($one)];
        }
        $return = preg_replace(&#39;/^0*/&#39;, &#39;&#39;, implode(&#39;&#39;, $hex64));
        if($len) {
            $clen = strlen($return);
            if($clen >= $len) {
                return $return;
            }
            else {
                return str_pad($return, $len, &#39;0&#39;, STR_PAD_LEFT);
            }
        }
        return $return;
    }
    /**
     * 功能和PHP原生函数str_split接近，只是从尾部开始计数切割
     * @param $str string 需要切割的字符串
     * @param $len integer 每段字符串的长度
     * @return array
     * @author 野马
     */
    function str_rsplit($str, $len = 1) {
        if($str == null || $str == false || $str == &#39;&#39;) return false;
        $strlen = strlen($str);
        if($strlen <= $len) return array($str);
        $headlen = $strlen % $len;
        if($headlen == 0) {
            return str_split($str, $len);
        }
        $return = array(substr($str, 0, $headlen));
        return array_merge($return, str_split(substr($str, $headlen), $len));
    }
$a=idate("U");
echo "\r\n<br />e:" . hex10to64($a);
echo "\r\n<br />e:" . hex64to10(hex10to64($a));

Algorithm 2:

The code is as follows:

function dec2s4($dec) {
    $base = '0123456789_$abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $result = '';
    do {
        $result = $base[$dec % 64] . $result;
        $dec = intval($dec / 64);
    } while ($dec != 0);
    return $result;
}
function  s42dec($sixty_four) {
    $base_map = array ( '0' => 0,    '1' => 1,    '2' => 2,    '3' => 3,    '4' => 4,    '5' => 5,    '6' => 6,    '7' => 7,    '8' => 8,    '9' => 9,    '_' => 10,    '$' => 11,    'a' => 12,    'b' => 13,    'c' => 14,    'd' => 15,    'e' => 16,    'f' => 17,    'g' => 18,    'h' => 19,    'i' => 20,    'j' => 21,    'k' => 22,    'l' => 23,    'm' => 24,    'n' => 25,    'o' => 26,    'p' => 27,    'q' => 28,    'r' => 29,    's' => 30,    't' => 31,    'u' => 32,    'v' => 33,    'w' => 34,    'x' => 35,    'y' => 36,    'z' => 37,    'A' => 38,    'B' => 39,    'C' => 40,    'D' => 41,    'E' => 42,    'F' => 43,    'G' => 44,    'H' => 45,    'I' => 46,    'J' => 47,    'K' => 48,    'L' => 49,    'M' => 50,    'N' => 51,    'O' => 52,    'P' => 53,    'Q' => 54,    'R' => 55,    'S' => 56,    'T' => 57,    'U' => 58,    'V' => 59,    'W' => 60,    'X' => 61,    'Y' => 62,    'Z' => 63,  );
    $result = 0;
    $len = strlen($sixty_four);
    for ($n = 0; $n < $len; $n++) {
        $result *= 64;
        $result += $base_map[$sixty_four{$n}];
    }
    return $result;
}
$a=idate("U");
var_dump(dec2s4($a));
var_dump(s42dec(dec2s4($a)));

Algorithm efficiency test:

The code is as follows:

$strarr = array();
$time1 = microtime(true);
for($i = 0; $i < 10000; ++$i) {
     $str = idate("U")+$i;
     $strarr[] = "{$i}->$str\r\n<br>";
 }
 $time2 = microtime(true);
 $time3 = $time2 - $time1;
 $time1 = microtime(true);
 for($i = 0; $i < 10000; ++$i) {
     $str = dec2s4(idate("U")+$i);
    $strarr[] = "{$i}->$str\r\n<br>";
}
$time2 = microtime(true);
echo "\r\n<br />运行10000次用时（秒）：" . ($time2 - $time1 - $time3);

测试结果
算法1：0.1687250137329
算法2：0.044965028762817
结论：算法1虽然效率上差一些，但是可以把md5生成的16进制转化为64进制，能够使用在必须使用md5的环境下缩短字符串。
六、总结
本文涉及了上传图片重命名可以能使用的几种方法，其中关键点是使用10进制转换为64进制来进行字符串的缩减。
例如，使用fast_uuid生成的17位数字，转换为64进制仅有7位字符;
具体使用，可以根据自身情况灵活使用，希望对大家有所帮助。

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