原字符串1,2,3,4,5,6,
去掉最后一个字符","，最终结果为1,2,3,4,5,6
代码如下：
$str = "1,2,3,4,5,6,";
$newstr = substr($str,0,strlen($str)-1);
echo $newstr;
//echo 1,2,3,4,5,6
系统自带的函数即可实现这样的效果，两种方法：
substr($str, 0, -1)
//函数2
rtrim($str, ",")
去掉前端几个字符
$arr1=substr($arr1,4);//去除前4个字符
去除数组中重复的元素值 array_unique()
<meta charset="utf-8" />
<?php
$a1="206,206,206,201,206,201";
//$array = explode(',', $a1); //字符串组成数组
$array1=implode(",",array_unique(explode(',', $a1)));
print_r($array1);
?>
数组索引值如何重新从0开始递增
<?php
$a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse");
print_r(array_values($a));
// 输出：
// Array ( [0] => Cat [1] => Dog [2] => Horse )
?>
截取去掉第一个字符
<?php
$a = "About us";
$a = substr($a,1);
echo $a;
?>
php取字符串的第一个字符
substr( $str, 0, 1 );
用法：
substr(string,start,length)
<?php
echo substr("Hello world",0,10)."<br>";
echo substr("Hello world",1,8)."<br>";
echo substr("Hello world",0,5)."<br>";
echo substr("Hello world",6,6)."<br>";
echo substr("Hello world",0,-1)."<br>";
echo substr("Hello world",-10,-2)."<br>";
echo substr("Hello world",0,-6)."<br>";
echo substr("Hello world",-2-3)."<br>";
?>
结果：
Hello worl
ello wor
Hello
world
Hello worl
ello wor
Hello
world