php 문자열 추출 substr > 프로그래밍

//기본사용법
$string = "Hello, world!";
$start = 7;

$substring = substr($string, $start);
echo $substring; // "world!"

//길이지정
$string = "Hello, world!";
$start = 7;
$length = 5;

$substring = substr($string, $start, $length);
echo $substring; // "world"

//시작 위치 음수
$string = "Hello, world!";
$start = -6;

$substring = substr($string, $start);

//길이 음수
$string = "Hello, world!";
$start = 0;
$length = -7;

$substring = substr($string, $start, $length);
echo $substring; // "Hello, "
echo $substring; // "world!"