trim()

Syntax

trim() returns a new string with unwanted characters removed from the beginning and end of $string. The original value is not changed.

Default behavior

Without a second argument, trim() removes these characters:

• an ordinary space (" ")
• a tab ("\t")
• a line feed ("\n")
• a carriage return ("\r")
• a vertical tab ("\v")
• the NUL byte ("\0")

This makes it a good first step when cleaning text that came from a form field, a line of text, or any other loosely formatted input.

<?php
$text = "\t  Hello, PHP!  \n";
$clean = trim($text);
var_dump($clean);

string(11) "Hello, PHP!"

The tab, spaces and newline around the text are removed. Whitespace between words is left untouched.

Custom character lists

The optional $characters argument is a list of individual characters, not a substring. trim() keeps removing any character from the list at either end until it reaches one that is not in the list.

You can also write a range with .., for example "\x00..\x1F" for the ASCII control characters.

When you pass your own list, the default whitespace characters are no longer included unless you list them too.

<?php
$path = "//docs/php//";
var_dump(trim($path, "/"));

$hello = "Hello World";
var_dump(trim($hello, "Hdle"));

var_dump(trim("abc", "bad"));
var_dump(trim("abc", "b"));

string(8) "docs/php"
string(5) "o Wor"
string(1) "c"
string(3) "abc"

The last two calls show a common surprise. In trim("abc", "bad"), the a is removed first, which puts b at the start so it is removed too. Only c remains. In trim("abc", "b"), the first and last characters are a and c, which are not in the list, so nothing is removed.

Related functions and tips

• ltrim() removes characters from the start only.
• rtrim() removes characters from the end only.
• str_replace() is the tool to use when you need to remove characters from the middle of a string.
• To clean every element of an array, apply trim() to each value, for example with array_map('trim', $values).
• trim() works on bytes, so it does not treat multibyte whitespace such as a non-breaking space as whitespace by default.