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Strings
PHP Manual

ltrim

(PHP 4, PHP 5)

ltrim — Strip whitespace (or other characters) from the beginning of a string

说明

string ltrim ( string $str [, string $charlist ] )

Strip whitespace (or other characters) from the beginning of a string.

参数

str

The input string.

charlist

You can also specify the characters you want to strip, by means of the charlist parameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters.

返回值

This function returns a string with whitespace stripped from the beginning of str . Without the second parameter, ltrim() will strip these characters:

  • " " (ASCII 32 (0x20)), an ordinary space.
  • "\t" (ASCII 9 (0x09)), a tab.
  • "\n" (ASCII 10 (0x0A)), a new line (line feed).
  • "\r" (ASCII 13 (0x0D)), a carriage return.
  • "\0" (ASCII 0 (0x00)), the NUL-byte.
  • "\x0B" (ASCII 11 (0x0B)), a vertical tab.

更新日志

版本 说明
4.1.0 The charlist parameter was added.

范例

Example#1 Usage example of ltrim()

<?php

$text = "\t\tThese are a few words :) ...  ";
$binary = "\x09Example string\x0A";
$hello  = "Hello World";
var_dump($text, $binary, $hello);

print "\n";


$trimmed = ltrim($text);
var_dump($trimmed);

$trimmed = ltrim($text, " \t.");
var_dump($trimmed);

$trimmed = ltrim($hello, "Hdle");
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);

?>

上例将输出：

string(32) "        These are a few words :) ...  "
string(16) "    Example string
"
string(11) "Hello World"

string(30) "These are a few words :) ...  "
string(30) "These are a few words :) ...  "
string(7) "o World"
string(15) "Example string
"

参见

Strings
PHP Manual