ltrim
(PHP 4, PHP 5)
ltrim — Strip whitespace (or other characters) from the beginning of a string
Description
string ltrim
( string
$str
[, string $character_mask
] )Strip whitespace (or other characters) from the beginning of a string.
Parameters
-
str -
The input string.
-
character_mask -
You can also specify the characters you want to strip, by means of the
character_maskparameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters.
Return Values
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.
Changelog
| Version | Description |
|---|---|
| 4.1.0 |
The character_mask parameter was added.
|
Examples
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($clean);
?>
The above example will output:
string(32) " These are a few words :) ... " string(16) " Example string " string(11) "Hello World" string(30) "These are a few words :) ... " string(30) "These are a few words :) ... " string(7) "o World" string(15) "Example string "
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Коментарии
To remove leading/trailing zeroes (example: "0123.4560"), doing a += 0 is easier than trim tricks.For those who use right-to-left languages such as Arabic, Hebrew, etc., it's worth mentioning that ltrim() (which stands for left trim) & rtrim() (which stands for right trim) DO NOT work contextually. The nomenclature is rather semantically incorrect. So in an RTL script, ltrim() will trim text from the right direction (i.e. beginning of RTL strings), and rtrim() will trim text from the left direction (i.e. end of RTL strings).Keep in mind the amount of resources preg_replace() uses.
I would suggest a simple if statement if you need to parse through large amounts of data.
<?php
function remove_leading_zeros_from_number($number_string) {
$limit = 9000.1
$temp = $number
(float) $temp;
if ($number < $limit) {
$number += 0;
} else {
preg_replace('~^[0]*([1-9][0-9]*)$~','$1',$number_string)
}
}
?>
Code is untested, but probably sound.
Guys, if += 0 is producing wrong values sometimes, and preg_replace is cpu consuming, then just stick to the main function described on that page, and use:<?php
$value = ltrim($value, '0');
?>
should be the fastest and most reliable.
I think all those comments can be misleading for begginers checking this page - it's sort of using magic tricks to reinvent the wheel.
+=0 not valid for something like 0000-5. Result is 0@scion4581
The problem is that the character mask (_stw in your case) isn't a literal string, but a character collection. So all characters within _stw are stripped. In your case this includes the w of weight also.
When using a $character_mask the trimming stops at the first character that is not on that mask.
So in the $string = "Hello world" example with $character_mask = "Hdle", ltrim($hello, $character_mask) goes like this:
1. Check H from "Hello world" => it is in the $character_mask, so remove it
2. Check e from "ello world" => it is in the $character_mask, so remove it
3. Check l from "llo world" => it is in the $character_mask, so remove it
4. Check l from "lo world" => it is in the $character_mask, so remove it
5. Check o from "o world" => it is NOT in the $character_mask, exit the function
Remaining string is "o world".
I hope it helps someone as I had a confusing moment with this function.
I noticed one thing.
Suppose you have to ltrim zeroes from strings like "015", "002", etc. and convert them back to numbers, eg. using intval.
Suppose you must convert to number "000" too.
In this case:
$trimmedString = ltrim('000', '0');
the value of $trimmedString would be NULL (and I think the docs should mention this).
Anyway, I initially thought I had to conditional check for this '000', but I found that intval(NULL) returns 0 (this thing is not in the docs of intval but is in a comment)