php常用内置函数-String
substr - 返回字符串的子串
- substr(string $string, int $offset, ?int $length = null): string
$str = 'hello world'; echo substr($str, -1); //d echo substr($str, 2, 5); //llo w
mb_substr - 获取部分字符串
- 定义
mb_substr( string $str, int $start, int $length = NULL, string $encoding = mb_internal_encoding() ): string
$str = '你好 世界'; echo mb_substr($str, 0, 2, 'UTF-8'); //你好
strrev - 字符串反转
strrev(string $string): string
$str = 'hello world'; echo strrev($str); //dlrow olleh
不使用内置函数的实现
$str = 'hello world'; $len = strlen($str); $rev_str = ''; for ($i=$len;$i>=0;$i--) { $rev_str .= $str[$i]; } echo $rev_str; //dlrow olleh
explode - 使用一个字符串分割另一个字符串
explode(string $separator, string $string, int $limit = PHP_INT_MAX): array
$str = 'hello world'; print_r(explode(' ', $str)); Array ( [0] => hello [1] => world )
implode - 用字符串连接数组元素
- implode(string
$separator
, array$array
): string$arr = ['hello', 'world']; echo implode(' ', $arr); //hello world
str_replace - 子字符串替换
- 定义
str_replace( mixed $search, mixed $replace, mixed $subject, int &$count = ? ): mixed //count是指替换的次数,默认全部替换
$str = 'hello world'; echo str_replace('world', 'php', $str); //hello php
substr_count - 计算字串出现的次数
- 定义
substr_count( string $haystack, string $needle, int $offset = 0, ?int $length = null ): int
$str = 'hello world'; echo substr_count($str, 'o'); //2
trim - 去除字符串首尾处的空白字符(或者其他字符)
- trim(string $str, string $character_mask = “ \t\n\r\0\x0B”): string
$str = ' hello world '; echo trim($str); //hello world
strrpos — 计算指定字符串在目标字符串中最后一次出现的位置
- strrpos — 计算指定字符串在目标字符串中最后一次出现的位置
$str = 'test.xxx.jpg'; echo strrpos($str, '.'); //8 //获取文件类型 echo substr($str, strrpos($str, '.')); //.jpg
preg_match - 执行匹配正则表达式
- 定义
preg_match( string $pattern, string $subject, array &$matches = null, int $flags = 0, int $offset = 0 ): int|false
$str = 'test.xxx.jpg'; echo preg_match('/(\.)+/', $str, $matches); //1 print_r($matches); Array ( [0] => . [1] => . )
str_pad - 使用另一个字符串填充字符串到指定长度
- 定义
str_pad( string $input, int $pad_length, string $pad_string = " ", int $pad_type = STR_PAD_RIGHT ): string
$str = '95'; echo str_pad($str, 4, '19', STR_PAD_LEFT); //1995
strtolower — 将字符串转化为小写
- strtolower(string $string): string
$str = 'Hello World!'; echo strtolower($str); //hello world!
strtoupper — 将字符串转化为大写
- strtoupper(string $string): string
$str = 'Hello World!'; echo strtolower($str); //HELLO WORLD!
strstr - 查找字符串的首次出现
- strstr(string $haystack, mixed $needle, bool $before_needle = false): string
$str = 'xxx@gmail.com'; echo strstr($str, '@'); //@gmail.com echo substr(strstr($str, '@'), 1); //gmail.com
htmlspecialchars - 将特殊字符转化为html实体
- 定义
htmlspecialchars( string $string, int $flags = ENT_COMPAT | ENT_HTML401, string $encoding = ini_get("default_charset"), bool $double_encode = true ): string
$str = '<scritp>alert("s")</script>'; echo htmlspecialchars($str); //<scritp>alert("s")</script>
htmlspecialchars_decode - 将特殊的 HTML 实体转换回普通字符
- htmlspecialchars_decode(string $string, int $flags = ENT_COMPAT | ENT_HTML401): string
$str = '<scritp>alert("s")</script>'; echo htmlspecialchars_decode($str); //<scritp>alert("s")</script>
str_split - 将字符串转换为数组
- str_split(string $string, int $split_length = 1): array
$str = 'hello world'; print_r(str_split($str, 4)); Array ( [0] => hell [1] => o wo [2] => rld )
number_format - 以千位分隔符方式格式化一个数字
- number_format(float $number, int $decimals = 0): string
$num = 1234567; echo number_format($num); //1,234,567
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