php常用[字符串]函数

nl2br 
功能：化换行符为<br>

<?php

$str = "cat isn't \n dog";

$result = nl2br($str);

echo $result;

/**结果

cat isn't

dog

*/

 

rtrim
功能：清除右边的空白

<?php

$str = "Hello world   ";

echo strlen($str)."<br>";

$result = rtrim($str);

echo strlen($result);

/**结果

14

11

*/

 

strip_tags
功能：清除字符串中html和php的标记

<?php

$str = "<font color = 'red'>Hello world</font>";

$result = strip_tags($str);

echo $result;

/**结果

Hello world

*/

 

strtolower
strtoupper
功能：转换成大小写

<?php

$str = "Hello World!";

$result = strtolower($str);

echo $result."<br>";



$result = strtoupper($str);

echo $result;

/**结果

hello world!

HELLO WORLD!

*/

 

trim
功能：去除首尾空格

<?php

$str = "  Hello World!  ";

$result = trim($str);

echo $str."<br>";

echo $result."<br>";

echo strlen($str)."<br>";

echo strlen($result);

/**结果

Hello World!

Hello World!

16

12

*/

 

str_ireplace
功能：替换

<?php

$str = "zhang san";

$result = str_ireplace("zhang","li",$str);

echo $str."<br>";

echo $result;

/**结果

zhang san

li san

*/

 

str_repeat
功能：将一个字符串重复多遍

<?php

$str = "Hello jiqing!";

$result = str_repeat($str,4);

echo $str."<br>";

echo $result;

/**结果

Hello jiqing!

Hello jiqing!Hello jiqing!Hello jiqing!Hello jiqing!

*/

 

str_replace
功能：区分大小写的替换

<?php

$str = "hello jiqing!";

$result1 = str_ireplace("Hello","Hi",$str); //不区分大小写

$result2 = str_replace("Hello","Hi",$str);  //区分大小写

echo $str."<br>";

echo $result1."<br>";

echo $result2."<br>";

/**结果

hello jiqing!

Hi jiqing!

hello jiqing!

*/

 

str_word_count
功能：返回字符串中单词的个数

<?php

$str = "hello jiqing a!";

$result1 = str_word_count($str);    //返回个数

$result2 = str_word_count($str,1);  //返回数组

echo $str."<br>";

echo $result1."<br>";

print_r($result2);

/**结果

hello jiqing a!

3

Array ( [0] => hello [1] => jiqing [2] => a )

*/

 

strlen
功能：返回字符串长度

<?php

$str = "hello jiqing a!";

$result = strlen($str);

echo $result;

/**结果

15

*/

 

substr_count
功能：计算一个字符串在另一个字符串中的个数

<?php

$str = "hello jiqing ,hello jim!";

$result = substr_count($str,"hello");

echo $result;

/**结果

2

*/

 

substr_replace
功能：从某个位置开始替换

<?php

$str = "hello jiqing ,hello jim!";

$result = substr_replace($str,"zhangsan",6);

echo $result."<br>";

$result = substr_replace($str,"zhangsan",6,6);//从某个位置替换，替换几个字符串

echo $result;

/**结果

hello zhangsan

hello zhangsan ,hello jim!

*/

 

substr
功能：获取子字符串

<?php

$str = "abcdef";

$result = substr($str,0,1); //从第0个开始，获取1个

echo $result."<br>";

$result = substr($str,0,-1);//从第0个开始，获取到除了最后一个的字符串

echo $result."<br>";

$result = substr($str,2,-1);//从第2个开始，获取到除了最后一个的字符串

echo $result."<br>";

$result = substr($str,-3,-1);//从第-3个开始，获取到除了最后一个的字符串

echo $result."<br>";

$result = substr($str,-3,1);//从第-3个开始，获取到除了最后一个的字符串

echo $result."<br>";

/**结果

a

abcde

cde

de

d

*/

 implode
功能：将数组转化为字符串

<?php

$array = array("2013","6","3");

$date = implode("/",$array);

echo $date;

/**结果

2013/6/3

*/

md5
功能：对字符串进行md5加密

<?php

$str = "Hello world";

$result = md5($str);

echo $result;

/**结果

3e25960a79dbc69b674cd4ec67a72c62

*/