php中字符串常用方法

1.ltrim();删去字符串中的前导空格；

$string1 = " zhangsan";
$result = ltrim($string1);
var_dump($result);

2.rtrim();用来删去字符串中的后缀空格；

$string2 = " zhang san ";
$result = rtrim($string2);
var_dump($result);

3.trim();截取字符串中首尾空格；

$string3 = " zhang san ";
$result = trim($string3);
var_dump($result);

4.str_pad();按需求对字符串进行填充；需添加四项参数，第一项为被填充的字符串，第二项为填充后字符串长度，第三项为填充的内容，第四项为填充位置（STR_PAD_LEFT,STR_PAD_RIGHT,STR_PAD_BOTH）;

$string4 = "zhangsan";
$result = str_pad($string4,12,"-=",STR_PAD_LEFT);
var_dump($result);

5.strtolower();将字符串全部变成小写；

$string5 = "ZHANGSAN";
$result = strtolower($string5);
var_dump($result);

6.strtoupper();将字符串全部变成大写；

$string6 = "zhangsan";
$result = strtoupper($string6);
var_dump($result);

7.ucfirst();将字符串第一个字符改大写；

$string7 = "zhangsan";
$result = ucfirst($string7);
var_dump($result);

8.ucwords();将字符串给个字第一个字符改大写；

$string8 = "zhang san";
$result = ucwords($string8);
var_dump($result);

9.nl2br();将字符串中\n转成HTML换行符<br/>;

$string9 = "zhang\nsan";
$result = nl2br($string9);
var_dump($string8);
var_dump($result);

10.strip_tags();删除HTML标签函数；

$string10 = "<P>zhangsan</P>";
$result = strip_tags($string10);
var_dump($string10);
var_dump($result);

11.strrev();将字符串前后颠倒；

$string11 = "zhangsan";
$result = strrev($string11);
var_dump($string11);
var_dump($result);

12.strlen();取得字符串长度；

$string12 = "zhangsan";
$result = strlen($string12);
var_dump($result);

13.md();加密函数；

$string13 = "zhangsan";
$result = md5($string13);
var_dump($result);

14.strcmp();按字节比较字符串是否相同，返回结果为前面字符串长度减去后面字符串长度

$string14 = "zhangsa";
$string15 = "zhangsan";
$result = strcmp($string14,$string15);
echo $result;

15.strncmp();比较指定长度的字符串；

$string16 = "zhangsa";
$string17 = "zanngsan";
$result = strncmp($string16,$string17,2);
echo $result;

16.strcasecmp();不区分大小写的全串比较；

$string18 = "Zhangsan";
$string19 = "zhangsan";
$result = strcasecmp($string18,$string19);
echo $result;

17.strnatcmp();按自然排序法时字符串的比较；

$string20 = "21zhangsan";
$string21 = "12zhangsan";
$result = strnatcmp($string20,$string21);
echo $result;

18.similar_text();字符串的模糊比较，返回相似字符串的个数；

$string22 = "zangsan";
$string23 = "zhangsan";
$result = similar_text($string22,$string23,$percent);
echo $percent;