字符串与ascii的转换

 字符串中只能包含字符，特殊符号不行。

//字符串转化为ascii

function  str2asc( $str ){     $num = '' ;     while ( strlen ( $str ) != 0 )    {         $a = substr ( $str , 0 , 1 );         $num .= ord ( $a );         $str = substr ( $str , 1 , strlen ( $str ));    }     return   $num ;}

//ascii转化为字符串

function  asc2str( $num ){     $num = ( string ) $num ;     $str = '' ;     while ( strlen ( $num ) != 0 )    {         $a = (int) substr ( $num , 0 , 1 );         if ( $a > 2 )        {             $b = (int) substr ( $num , 0 , 2 );             $num = substr ( $num , 2 , strlen ( $num ));        } else         {             $b = (int) substr ( $num , 0 , 3 );             $num = substr ( $num , 3 , strlen ( $num ));        }         $str .= chr ( $b );    }     return   $str ;}

示例: echo str2asc( 'sfdsl '); echo  ' <br > '; echo asc2str(str2asc( 'sfdsl ')); --------------------- 115102100115108 sfdsl 

注：调用asc2str( '123456 ') 不能asc2str(123456) ，也就是要将123456转化为字符串。