substr
(PHP 4, PHP 5)
substr — Return part of a string
Description
Returns the portion of string specified by the start and length parameters.
Parameters
- string
-
The input string. Must be one character or longer.
- start
-
If start is non-negative, the returned string will start at the start'th position in string, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.
If start is negative, the returned string will start at the start'th character from the end of string.
If string is less than or equal to start characters long, FALSE will be returned.
Example #1 Using a negative start
<?php
$rest = substr("abcdef", -1); // returns "f"
$rest = substr("abcdef", -2); // returns "ef"
$rest = substr("abcdef", -3, 1); // returns "d"
?> - length
-
If length is given and is positive, the string returned will contain at most length characters beginning from start (depending on the length of string).
If length is given and is negative, then that many characters will be omitted from the end of string (after the start position has been calculated when a start is negative). If start denotes the position of this truncation or beyond, false will be returned.
If length is given and is 0, FALSE or NULL an empty string will be returned.
If length is omitted, the substring starting from start until the end of the string will be returned.
Example #2 Using a negative length
<?php
$rest = substr("abcdef", 0, -1); // returns "abcde"
$rest = substr("abcdef", 2, -1); // returns "cde"
$rest = substr("abcdef", 4, -4); // returns false
$rest = substr("abcdef", -3, -1); // returns "de"
?>
Return Values
Returns the extracted part of string, or FALSE on failure or an empty string.
Changelog
Version | Description |
---|---|
5.2.2 | If the start parameter indicates the position of a negative truncation or beyond, false is returned. Prior to this version, an empty string was returned. |
Examples
Example #3 Basic substr() usage
<?php
echo substr('abcdef', 1); // bcdef
echo substr('abcdef', 1, 3); // bcd
echo substr('abcdef', 0, 4); // abcd
echo substr('abcdef', 0, 8); // abcdef
echo substr('abcdef', -1, 1); // f
// Accessing single characters in a string
// can also be achieved using "square brackets"
$string = 'abcdef';
echo $string[0]; // a
echo $string[3]; // d
echo $string[strlen($string)-1]; // f
?>
Example #4 substr() casting behaviour
<?php
class apple {
public function __toString() {
return "green";
}
}
echo "1) ".var_export(substr("pear", 0, 2), true).PHP_EOL;
echo "2) ".var_export(substr(54321, 0, 2), true).PHP_EOL;
echo "3) ".var_export(substr(new apple(), 0, 2), true).PHP_EOL;
echo "4) ".var_export(substr(true, 0, 1), true).PHP_EOL;
echo "5) ".var_export(substr(false, 0, 1), true).PHP_EOL;
echo "6) ".var_export(substr("", 0, 1), true).PHP_EOL;
echo "7) ".var_export(substr(1.2e3, 0, 4), true).PHP_EOL;
?>
The above example will output:
1) 'pe' 2) '54' 3) 'gr' 4) '1' 5) false 6) false 7) '1200'
Errors/Exceptions
Returns FALSE on error.
<?php
var_dump(substr('a', 1)); // bool(false)
?>
See Also
- strrchr() - Find the last occurrence of a character in a string
- substr_replace() - Replace text within a portion of a string
- preg_match() - Perform a regular expression match
- trim() - Strip whitespace (or other characters) from the beginning and end of a string
- mb_substr() - Get part of string
- wordwrap() - Wraps a string to a given number of characters
- String access and modification by character