function strtohex（$ string）
 {
 $ string = str_split （$ string）; 
 foreach（$ string as& $ char）
 $ char =\x.dechex（ord（$ char））; 
 return implode（''，$ string）; 
} 

 print strtohex（[0-9A-Za-z\ + / =] *）; 
 

上述代码会给你

  \x5b\x30\x2d\x39\x41\x2d\x5a\x61\x2d\x7a\x5c\x2b\x2f\ x3d \x5d\x2a 
 

我知道它看起来不像输出expect，但是似乎不是字符串到十六进制。

I have a string like that:

[0-9A-Za-z\+/=]*

How can I converted in the following form:

"\133\x30\55\x39\101\x2d\132\x61\55\x7a\134\x2b\57\x3d\135\x2a"

Is there any function for that ?

function strtohex($string)
{
  $string = str_split($string);
  foreach($string as &$char)
    $char = "\x".dechex(ord($char));
  return implode('',$string);
}

print strtohex("[0-9A-Za-z\+/=]*");

The above code will give you

\x5b\x30\x2d\x39\x41\x2d\x5a\x61\x2d\x7a\x5c\x2b\x2f\x3d\x5d\x2a

I'm aware that it doesn't look like the output you expect, but that doesn't seem to be string to hex at all.