trim
(PHP 4, PHP 5)
trim — 去除字符串首尾处的空白字符（或者其他字符）
说明
string trim
( string $str
[, string $charlist = " tnr x0B"
] )
此函数返回字符串 str 去除首尾空白字符后的结果。如果不指定第二个参数，trim() 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。
" " (ASCII 0
(0x00))，空字节符。
"x0B" (ASCII 11
(0x0B))，垂直制表符。
参数
str
待处理的字符串。
charlist
可选参数，过滤字符也可由 charlist 参数指定。一般要列出所有希望过滤的字符，也可以使用 “..” 列出一个字符范围。
返回值
过滤后的字符串。
更新日志
版本
说明
4.1.0
新增可选的 charlist 参数。
范例
Example #1 trim() 使用范例
<?php
$text = "ttThese are a few words :) ... ";
$binary = "x09Example stringx0A";
$hello = "Hello World";
var_dump($text, $binary, $hello);
print "n";
$trimmed = trim($text);
var_dump($trimmed);
$trimmed = trim($text, " t.");
var_dump($trimmed);
$trimmed = trim($hello, "Hdle");
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($clean);
?>
以上例程会输出：
string(32) " These are a few words :) ... " string(16) " Example string " string(11) "Hello World" string(28) "These are a few words :) ..." string(24) "These are a few words :)" string(5) "o Wor" string(14) "Example string"
Example #2 使用 trim() 清理数组值
<?php
function trim_value(&$value)
{
$value = trim($value);
}
$fruit = array('apple','banana ', ' cranberry ');
var_dump($fruit);
array_walk($fruit, 'trim_value');
var_dump($fruit);
?>
以上例程会输出：
array(3) {
[0]=>
string(5) "apple"
[1]=>
string(7) "banana "
[2]=>
string(11) " cranberry "
}
array(3) {
[0]=>
string(5) "apple"
[1]=>
string(6) "banana"
[2]=>
string(9) "cranberry"
}
注释
Note:
Possible gotcha: removing middle characters
Because trim() trims characters from the beginning and end of a string, it may be confusing when characters are (or are not) removed from the middle. trim('abc', 'bad') removes both 'a' and 'b' because it trims 'a' thus moving 'b' to the beginning to also be trimmed. So, this is why it "works" whereas trim('abc', 'b') seemingly does not.
参见
ltrim() - 删除字符串开头的空白字符（或其他字符） rtrim() - 删除字符串末端的空白字符（或者其他字符） str_replace() - 子字符串替换