substr()选读和修改子串

$value = substr($string, $offset, $count);
$value = substr($string, $offset);

substr($string, $offset, $count) = $newstring;
substr($string, $offset, $count, $newstring); # same as previous
substr($string, $offset) = $newtail;

$string = "good good start, day day up!";
substr($string, 0, 4) = "bad";
print $string;

bad good start, day day up!

$string = "good good start, day day up!";
substr($string, 5, 4, "bad");
print $string;

good bad start, day day up!

 

 

$string = "good good start, day day up!";
substr($string, 0) = "bad";
print $string;

bad