ltrim

(PHP 4, PHP 5, PHP 7, PHP 8)

ltrim — Retira espacios en blanco (u otros caracteres) del inicio de un string

Descripción

ltrim(string $str, string $character_mask = ?): string

Retira espacios en blanco (u otros caracteres) del inicio de un string.

Parámetros

str: El string de entrada.
character_mask: Se puede también especificar los caracteres que se desean retirar por medio del parámetro character_mask. Simplemente se listan todos los caracteres que se quieren retirar. Con .. se puede especificar un rango de caracteres.

Valores devueltos

Esta función devuelve un string con los espacios en blanco retirados del inicio de str. Sin el segundo parámetro, ltrim() retirará estos caracteres:

" " (ASCII 32 (0x20)), un espacio ordinario.
"\t" (ASCII 9 (0x09)), un tabulador.
"\n" (ASCII 10 (0x0A)), una nueva línea (line feed).
"\r" (ASCII 13 (0x0D)), un retorno de carro.
"\0" (ASCII 0 (0x00)), el byte NULL.
"\x0B" (ASCII 11 (0x0B)), un tabulador vertical.

Ejemplos

Ejemplo #1 Ejemplo de uso de 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);

// retira los caracteres ASCII de control al inicio de $binary
// (de 0 a 31 inclusive)
$clean = ltrim($binary, "\x00..\x1F");
var_dump($clean);

?>

El resultado del ejemplo sería:

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
"

Ver también

trim() - Elimina espacio en blanco (u otro tipo de caracteres) del inicio y el final de la cadena
rtrim() - Retira los espacios en blanco (u otros caracteres) del final de un string

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User Contributed Notes 3 notes

down

tavi undersc 10 from yahoocom ¶

9 years ago

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.

down

Usamah M dot Ali (usamah1228 at gmail dot com) ¶

16 years ago

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).

down

dzek dot remove_this at dzek dot eu ¶

13 years ago

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.

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