对于任何带ord的字符（$ char）< 16你得到一个只有1长的HEX。

 <？php 
 function strToHex（$ string）{
 $ hex =''; （$ i = 0; $ i< strlen（$ string）; $ i ++）{
 $ ord = ord（$ string [$ i]）; 
。 
 $ hexCode = dechex（$ ord）; 
 $ hex。= substr（'0'。$ hexCode，-2）; 
} 
 return strToUpper（$ hex）; 
} 
函数hexToStr（$ hex）{
 $ string =''; 
 for $（$ i = 0; $ i  $ string。= chr（hexdec（$ hex [$ i]。$ hex [$ I + 1]））; 
} 
 return $ string; 
} 


 //测试
 header（'Content-Type：text / plain'）; 
函数测试（$ expected，$ actual，$ success）{
 if（$ expected！== $ actual）{
 echoExpected：'$ expected'\\\
; 
 echoActual：'$ actual'\\\
; 
回声\\\
; 
 $ success = false; 
} 
返回$ success; 
} 

 $成功= true; 
 $ success = test（'00'，strToHex（hexToStr（'00'）），$ success）; 
 $ success = test（'FF'，strToHex（hexToStr（'FF'）），$ success）; 
 $ success = test（'000102FF'，strToHex（hexToStr（'000102FF'）），$ success）; 
 $ success = test（'↕↑↔§P↔§P♫§T↕§↕'，hexToStr（strToHex（'↕↑↔§P↔§P♫§T↕§↕'）），$成功）; 

 echo $ success？ 成功：\失败; 
 

I got the problem when convert between this 2 type in PHP. This is the code I searched in google

function strToHex($string){
    $hex='';
    for ($i=0; $i < strlen($string); $i++){
        $hex .= dechex(ord($string[$i]));
    }
    return $hex;
}


function hexToStr($hex){
    $string='';
    for ($i=0; $i < strlen($hex)-1; $i+=2){
        $string .= chr(hexdec($hex[$i].$hex[$i+1]));
    }
    return $string;
}

I check it and found out this when I use XOR to encrypt.

I have the string "this is the test", after XOR with a key, I have the result in string ↕↑↔§P↔§P ♫§T↕§↕. After that, I tried to convert it to hex by function strToHex() and I got these 12181d15501d15500e15541215712. Then, I tested with the function hexToStr() and I have ↕↑↔§P↔§P♫§T↕§q. So, what should I do to solve this problem? Why does it wrong when I convert this 2 style value?

For any char with ord($char) < 16 you get a HEX back which is only 1 long. You forgot to add 0 padding.

This should solve it:

<?php
function strToHex($string){
    $hex = '';
    for ($i=0; $i<strlen($string); $i++){
        $ord = ord($string[$i]);
        $hexCode = dechex($ord);
        $hex .= substr('0'.$hexCode, -2);
    }
    return strToUpper($hex);
}
function hexToStr($hex){
    $string='';
    for ($i=0; $i < strlen($hex)-1; $i+=2){
        $string .= chr(hexdec($hex[$i].$hex[$i+1]));
    }
    return $string;
}


// Tests
header('Content-Type: text/plain');
function test($expected, $actual, $success) {
    if($expected !== $actual) {
        echo "Expected: '$expected'\n";
        echo "Actual:   '$actual'\n";
        echo "\n";
        $success = false;
    }
    return $success;
}

$success = true;
$success = test('00', strToHex(hexToStr('00')), $success);
$success = test('FF', strToHex(hexToStr('FF')), $success);
$success = test('000102FF', strToHex(hexToStr('000102FF')), $success);
$success = test('↕↑↔§P↔§P ♫§T↕§↕', hexToStr(strToHex('↕↑↔§P↔§P ♫§T↕§↕')), $success);

echo $success ? "Success" : "\nFailed";