(PHP 4, PHP 5, PHP 7)
trim — 去除字符串首尾处的空白字符（或者其他字符）
$str
[, string $character_mask = " \t\n\r\0\x0B"
] ) : string
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：
32
(0x20))，普通空格符。
9
(0x09))，制表符。
10
(0x0A))，换行符。
13
(0x0D))，回车符。
0
(0x00))，空字节符。
11
(0x0B))，垂直制表符。
str待处理的字符串。
character_mask
可选参数，过滤字符也可由 character_mask 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。
过滤后的字符串。
Example #1 trim() 使用范例
<?php
$text = "\t\tThese are a few words :) ... ";
$binary = "\x09Example string\x0A";
$hello = "Hello World";
var_dump($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"
}
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" whereastrim('abc', 'b')seemingly does not.