PHP judges the string encoding type

Two functions collected

First, I found that it was not good enough in my tests, and most of them were accurate.

 //  Returns true if $ string is valid UTF-8 and false otherwise.  
  Function  Is_utf8_bak (  $ Word  ){
  If  (  Preg_match  (  "  /^ ([  "  . CHR  (  228  )  .  "  -  "  .  CHR  (  233  )  .  "  ] {1 }[  "  . CHR  (  128  )  .  "  -  "  .  CHR  (  191  )  .  "  ] {1 }[  "  . CHR  (  128  )  .  "  -  "  .  CHR  (  191  )  .  "  ] {1}) {1 }/  "  , $ Word  )  =     True     |     Preg_match  (  "  /([  "  .  CHR  (  228  ) .  "  -  "  .  CHR  (  233  )  .  "  ] {1 }[  "  .  CHR  (  128  ) .  "  -  "  .  CHR  (  191  )  .  "  ] {1 }[  "  .  CHR  (  128  ) .  "  -  "  .  CHR  (  191  )  .  "  ] {1}) {1} $/  "  ,  $ Word  )  =    True     |     Preg_match  (  "  /([  "  .  CHR  (  228  )  .  "  -  " .  CHR  (  233  )  .  "  ] {1 }[  "  .  CHR  (  128  )  .  "  -  " .  CHR  (  191  )  .  "  ] {1 }[  "  .  CHR  (  128  )  .  "  -  " .  CHR  (  191  )  .  "  ] {1}) {2 ,}/  "  ,  $ Word  )  =     True  )
{
  Return    True  ;
}  Else  {
  Return     False  ;
}
} 

The second test is better than the first one.

 //  Returns true if $ string is valid UTF-8 and false otherwise.  
  Function  Is_utf8 (  $ String  ){

 //  From http://w3.org/International/questions/qa-forms-utf-8.html  
    Return     Preg_match  (  ' % ^ (? :
[\ X09 \ x0a \ x0d \ x20-\ x7e] # ASCII
| [\ Xc2-\ xdf] [\ X80-\ xbf] # non-overlong 2-byte
| \ Xe0 [\ xa0-\ xbf] [\ X80-\ xbf] # excluding overlongs
| [\ Xe1-\ xec \ xee \ XeF] [\ X80-\ xbf] {2} # Straight 3-byte
| \ Xed [\ X80-\ x9f] [\ X80-\ xbf] # excluding Surrogates
| \ Xf0 [\ x90-\ xbf] [\ X80-\ xbf] {2} # Planes 1-3
| [\ Xf1-\ xf3] [\ X80-\ xbf] {3} # planes 4-15
| \ Xf4 [\ X80-\ x8f] [\ X80-\ xbf] {2} # plane 16
) * $ % XS  '  ,     $ String  );

}  //  Function is_utf8