String Funkcje
PHP Manual

substr

(PHP 4, PHP 5)

substrReturn part of a string

Opis

string substr ( string $string , int $start [, int $length ] )

Returns the portion of string specified by the start and length parameters.

Parametry

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", -31); // 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"
?>

Zwracane wartości

Returns the extracted part of string; lub FALSE w przypadku niepowodzenia, or an empty string.

Rejestr zmian

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.

Przykłady

Przykład #3 Basic substr() usage

<?php
echo substr('abcdef'1);     // bcdef
echo substr('abcdef'13);  // bcd
echo substr('abcdef'04);  // abcd
echo substr('abcdef'08);  // abcdef
echo substr('abcdef', -11); // 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"02), true).PHP_EOL;
echo 
"2) ".var_export(substr(5432102), true).PHP_EOL;
echo 
"3) ".var_export(substr(new apple(), 02), true).PHP_EOL;
echo 
"4) ".var_export(substr(true01), true).PHP_EOL;
echo 
"5) ".var_export(substr(false01), true).PHP_EOL;
echo 
"6) ".var_export(substr(""01), true).PHP_EOL;
echo 
"7) ".var_export(substr(1.2e304), true).PHP_EOL;
?>

Powyższy przykład wyświetli:

1) 'pe'
2) '54'
3) 'gr'
4) '1'
5) false
6) false
7) '1200'

Błędy/Wyjątki

Returns FALSE on error.

<?php
var_dump
(substr('a'1)); // bool(false)
?>

Zobacz też:


String Funkcje
PHP Manual