ltrim、rtrim与 trim 函数
返回 Variant (String),其中包含指定字符串的拷贝,没有前导空白 (ltrim)、尾随空白 (rtrim) 或前导和尾随空白 (trim)。语法ltrim(string)rtrim(string)trim(string)必要的 string 参数可以是任何有效的字符串表达式。如果 string 包含 Null,将返回 Null。 ltrim、rtrim 和 trim 函数的区别 返回不带前导空格 (ltrim)、后续空格 (rtrim) 或前导与后续空格 (trim) 的字符串副本。 ltrim(string) rtrim(string) trim(string) string 参数是任意有效的字符串表达式。如果 string 参数中包含 Null,则返回 Null。下面的示例利用 ltrim, rtrim, 和 trim 函数分别用来除去字符串开始的空格、尾部空格、 开始和尾部空格:
$MyVar = ltrim(" vbscript ") //$MyVar 包含 "vbscript "。
$MyVar = rtrim(" vbscript ") //$MyVar 包含 " vbscript"$MyVar = trim(" vbscript ") //$MyVar 包含 "vbscript"===========
string trim ( string $str [, string $charlist ] )
//去除首尾空白字符string ltrim ( string $str [, string $charlist ] )//去除左边空白字符string rtrim ( string $str [, string $charlist ] )//去除右边空白字符这些函数返回字符串 str 去除空白字符后的结果。如果不指定第二个参数,3个函数将去除这些字符:
" " (ASCII 32 (0x20)),普通空格符。
"\t" (ASCII 9 (0x09)),制表符。 "\n" (ASCII 10 (0x0A)),换行符。 "\r" (ASCII 13 (0x0D)),回车符。 "\0" (ASCII 0 (0x00)),空字节符。 "\x0B" (ASCII 11 (0x0B)),垂直制表符。通过指定 charlist,可以指定想要删除的字符列表。简单地列出你想要删除的全部字符。使用 .. 格式,可以指定一个范围。
$text = "\t\tThese are a few words :) ... ";$binary = "\x09Example string\x0A";
//\x09是\t,\xoA是\n$hello = "Hello World";var_dump($text, $binary, $hello);
输出:
tring(32) " These are a few words :) ... "string(16) " Example string"string(11) "Hello World"
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trim的用法:
$trimmed = trim($text);var_dump($trimmed);$trimmed = trim($text, " \t.");
//清除所有的\t和.var_dump($trimmed);$trimmed = trim($hello, "Hdle");//清除所有的H、d、l和e
var_dump($trimmed);// 清除 $binary 首位的 ASCII 控制字符// (包括 0-31)$clean = trim($binary, "\x00..\x1F");var_dump($clean);
输出:
string(28) "These are a few words :) ..."string(24) "These are a few words :)"string(5) "o Wor"string(14) "Example string"-----------------
ltrim的用法:
$trimmed = ltrim($text);var_dump($trimmed);$trimmed = ltrim($text, " \t.");
//清除左端的\t和.
var_dump($trimmed);$trimmed = ltrim($hello, "Hdle");//清除左端的H、d、l和e
var_dump($trimmed);// trim the ASCII control characters at the beginning of $binary// (from 0 to 31 inclusive)$clean = ltrim($binary, "\x00..\x1F");var_dump($clean);输出:string(30) "These are a few words :) ... "string(30) "These are a few words :) ... "string(7) "o World"string(15) "Example string"
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rtrim的用法:
$trimmed = rtrim($text);var_dump($trimmed);$trimmed = rtrim($text, " \t.");//清除右端的\t和.
var_dump($trimmed);$trimmed = rtrim($hello, "Hdle");
//清除右端的H、d、l和e
var_dump($trimmed);// 删除 $binary 末端的 ASCII 码控制字符// (包括 0 - 31)$clean = rtrim($binary, "\x00..\x1F");var_dump($clean);输出:string(30) " These are a few words :) ..."string(26) " These are a few words :)"string(9) "Hello Wor"string(15) " Example string"