1.echo strlen("hello");  //取字符串的长度

2.echo strcmp("hello","hello");  //用来比较两个字符串是否相等,区分大小写

 

3.echo strcasecmp( )；  //字符串比较，不区分大小写，相同返回0

4.echo strtolower("Hello");  //转小写

5.echo  strtoupper("hello");  //转大写

6.$s="hello,world,test";

$arr=explode(",",$s);  //将字符串s拆分，返回数组

7.$arr=array("111","222","333");

echo implode(",",$arr)  //将数组元素拼接成字符串

8.$s="hello world";

echo substr_replace($s,"*",0,2); //截取替换，指定位置替换

9.$s="hello world";

echo str_replace("l","*",$s); //查找替换,ctrl+f也可以实现

10.$s="hello world";

echo substr($s,0,5); //截取字符串