PHP removes the fewest characters into a palindrome string

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$s = "; for ($i =0; $i <15; $i + +) {    $s. =CHR (rand (97, 122));} $s = $string =  strtoupper ($s); Echo $string;

This is a randomly generated string

A string, removing the fewest characters to make it a palindrome    such as ABBA   Ababa  a  are palindrome//  ABSDFDA   Remove the fewest characters and form a palindrome into a   adfda// Focus on  the first and last character of the next string must be the same

Delete the value of a position in a string function Delete_str_pos ($str, $pos) {$s = Str_split ($STR);    Unset ($s [$pos]); Return implode ("", array_values ($s));}    The judgment is not a palindrome string function Is_huichuan ($s) {if (strlen ($s) ==1) {return true;        }else {$o = strlen ($s)/2;        $two = Floor ($o);        $a = substr ($s, 0, $two);        if (Is_float ($o)) {$b =substr ($s, $two + 1);        }else {$b =substr ($s, $two);        } if (Strtolower ($a) ==strtolower (Strrev ($b))) {return true; }} return false;}        The 2nd method of judging palindrome function Is_huiwen ($s) {if (Strtoupper ($s) = = Strtoupper (Implode ("", Array_reverse (Str_split ($s)))) {    return true; } return false;}    function Delete_pos ($str, $min, $max) {$s = Str_split ($STR);    if ($max > strlen ($str)) {$max = strlen ($STR);    } for ($i = $min; $i < $max; $i + +) {unset ($s [$i]); } Return Implode ("", array_values ($s));}    function Method1 ($string) {$end =-1;for ($i =0; $i <strlen ($string), $i + +) {if (Is_huichuan ($string)) {Header ("Content-type:text/ht            Ml;charset=utf-8 ");            echo "<br/>";            echo "is a palindrome";        Break        } $pos = Strrpos ($string, $string [$i], $end);  if (Is_numeric ($pos)) {//represents the first directly deleted character if ($pos = = $i) {$string = Delete_str_pos ($string, $pos);            Remove string $i--;            }elseif ($pos = = strlen ($string)-1) {//This time is the last string for palindrome $end = $end-1;            }else {$string = Delete_pos ($string, $pos +1,strlen ($string)-$i);            }}else {//If the character that was not found directly deleted $i is incorrect $string = Delete_str_pos ($string, $i);//Remove string        $i--;        } echo "<br/>";    Echo $string; }}