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(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.
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"
?>
Returns the extracted part of string; or FALSE
on failure, or
an empty string
.
Version | Description |
---|---|
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.
|
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'
Returns FALSE
on error.
<?php
var_dump(substr('a', 1)); // bool(false)
?>