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    ltrim

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

    ltrim — Rimuove gli spazi (o altri caratteri) dall'inizio di una stringa

    Descrizione

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

    Rimuove gli spazi (o altri caratteri) dall'inizio di una stringa

    Elenco dei parametri

    str

    La stringa di input.

    character_mask

    Si possono anche specificare i caratteri che si vogliono eliminare, mediante il parametro character_mask. È sufficiente elencare tutti i caratteri che vogliono essere eliminati. Con .. si può specificare un intervallo di caratteri.

    Valori restituiti

    Questa funzione restituisce una stringa con gli spazi eliminati dall'inzio della str. Senza il secondo parametro, ltrim() eliminerà questi caratteri:

    • " " (ASCII 32 (0x20)), uno spazio ordinario.
    • "\t" (ASCII 9 (0x09)), una tabulazione.
    • "\n" (ASCII 10 (0x0A)), una nuova linea (line feed).
    • "\r" (ASCII 13 (0x0D)), un ritorno a capo.
    • "\0" (ASCII 0 (0x00)), il byte NUL.
    • "\x0B" (ASCII 11 (0x0B)), una tab verticale.

    Esempi

    Example #1 Esempio d'uso di 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);

    // elimina i caratteri di controllo ASCII all'inizio di $binary
    // (da 0 a 31 compreso)
    $clean = ltrim($binary, "\x00..\x1F");
    var_dump($clean);

    ?>

    Il precedente esempio visualizzerà:

    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
"

    Vedere anche:

    • trim() - Rimuove gli spazi (ed altri caratteri) all'inizio e alla fine di un testo
    • rtrim() - Rimuove gli spazi (ed altri caratteri) dalla fine della stringa

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    User Contributed Notes 8 notes

    up
    84
    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.
    up
    21
    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).
    up
    6
    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.
    up
    -6
    mroeling at exed dot nl
    10 years ago
    @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.
    up
    -6
    Mauro
    7 years ago
    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)
    up
    -21
    John Sherwood
    18 years ago
    To remove leading/trailing zeroes (example: "0123.4560"), doing a += 0 is easier than trim tricks.
    up
    -15
    juan at ecogomera dot com
    11 years ago
    +=0 not valid for something like 0000-5. Result is 0
    up
    -30
    Mike
    13 years ago
    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.
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