substr

(PHP 4, PHP 5, PHP 7)

substr — Return part of a string

Descrierea

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

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

Parametri

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 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"
?>

Valorile întoarse

Returns the extracted part of string; sau FALSE în cazul eșecului, or an empty string.

Istoricul schimbărilor

Versiune Descriere
7.0.0 If string is equal to start characters long, an empty string will be returned. Prior to this version, FALSE was returned in this case.
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.

Exemple

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;
?>

Exemplul de mai sus va afișa în PHP 7:

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

Exemplul de mai sus va afișa în PHP 5:

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

Erori/Excepții

Returns FALSE on error.

<?php
var_dump(substr('a', 2)); // bool(false)
?>

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