(PHP 4, PHP 5)
substr — Return part of a string
$string
, int $start
[, int $length
] )
Returns the portion of string specified by the
start and length 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.
Przykład #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.
Przykład #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"
?>
Returns the extracted part of string; lub FALSE w przypadku niepowodzenia, or
an empty string.
| Wersja | Opis |
|---|---|
| 5.2.2 - 5.2.6 |
If the start parameter indicates the position of
a negative truncation or beyond, false is returned. Other versions get
the string from start.
|
Przykład #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
?>
Przykład #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;
?>
Powyższy przykład wyświetli:
1) 'pe' 2) '54' 3) 'gr' 4) '1' 5) false 6) false 7) '1200'
Returns FALSE on error.
<?php
var_dump(substr('a', 1)); // bool(false)
?>