Statement on glibc/iconv Vulnerability

    trim

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

    trim — Strip whitespace (or other characters) from the beginning and end of a string

    Description

    trim(string $string, string $characters = " \n\r\t\v\x00"): string

    This function returns a string with whitespace stripped from the beginning and end of string. Without the second parameter, trim() 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.
    • "\v" (ASCII 11 (0x0B)), a vertical tab.

    Parameters

    string

    The string that will be trimmed.

    characters

    Optionally, the stripped characters can also be specified using the characters parameter. Simply list all characters that you want to be stripped. With .. you can specify a range of characters.

    Return Values

    The trimmed string.

    Examples

    Example #1 Usage example of trim()

    <?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);

    $trimmed = trim($hello, 'HdWr');
    var_dump($trimmed);

    // trim the ASCII control characters at the beginning and end of $binary
    // (from 0 to 31 inclusive)
    $clean = trim($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(28) "These are a few words :) ..."
string(24) "These are a few words :)"
string(5) "o Wor"
string(9) "ello Worl"
string(14) "Example string"

    Example #2 Trimming array values with trim()

    <?php
    function trim_value(&$value)
    {
    $value = trim($value);
    }

    $fruit = array('apple','banana ', ' cranberry ');
    var_dump($fruit);

    array_walk($fruit, 'trim_value');
    var_dump($fruit);

    ?>

    The above example will output:

    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"
}

    Notes

    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" whereas trim('abc', 'b') seemingly does not.

    See Also

    • ltrim() - Strip whitespace (or other characters) from the beginning of a string
    • rtrim() - Strip whitespace (or other characters) from the end of a string
    • str_replace() - Replace all occurrences of the search string with the replacement string

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    User Contributed Notes 3 notes

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    12
    pcoates at yukon1000 dot com
    11 months ago
    note there is a behaviour change in php 8

    You used to be able to say:
    $p1 = trim($_POST['p1']);
    This will now throw deprecated warnings if parameter p1 is not set. It is better to say:
    $p1 = trim($_POST['p1']??'');
    or
    $p1 = isset($_POST['p1']) ? trim($_POST['p1']) : null;
    or
    $p1 = isset($_POST['p1']) ? trim($_POST['p1']) : '';
    up
    1
    gwyneth dot llewelyn at gwynethllewelyn dot net
    9 months ago
    Note that trim() is not aware of Unicode points that represent whitespace (e.g., in the General Punctuation block), except, of course, for the ones mentioned in this page.

    There is no Unicode-specific trim function in PHP at the time of writing (July 2023), but you can try some examples of trims using multibyte strings posted on the comments for the mbstring extension: https://www.php.net/manual/en/ref.mbstring.php
    up
    0
    zoad_aish at gmail dot com
    2 hours ago
    I wanted to bring to your attention a peculiar behavior in PHP that might catch some of us off guard, particularly when dealing with string manipulation.

    When using the trim() function in PHP with a variable assigned as null, the result might not be what you expect. Instead of returning null, trim() will actually return an empty string "".

    Here's a quick example to illustrate:
    $txt = null;
    var_dump($txt); // Outputs: NULL
    $txt = trim($txt);
    echo "<br>";
    var_dump($txt); // Outputs: string(0) ""

    As you can see, even though the initial value of $txt is null, after applying trim(), it becomes an empty string "".

    This behavior might seem counterintuitive at first, so it's important to keep it in mind, especially when handling user input or dealing with data that might contain null values.

    Understanding these nuances can save us from unexpected bugs and make our code more robust.
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