PHP5中文手册·Return part of a string -- 追寻梦想＞编程乐园＞PHP 编程

说明

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

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

参数

string

The input string.

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 .

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 string is less than or equal to start characters long, FALSE will be returned.

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 a position beyond this truncation, an empty 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 ""
$rest = substr("abcdef", -3, -1); // returns "de"
?>

返回值

Returns the extracted part of string.

范例

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 achived using "curly braces"
$string = 'abcdef';
echo $string{0};                 // a
echo $string{3};                 // d
echo $string{strlen($string)-1}; // f

?>


	PHP5中文手册 substr_replace trim Strings PHP Manual substr (PHP 4, PHP 5) substr — Return part of a string 说明 string substr ( string `$string` , int `$start` [, int `$length` ] ) Returns the portion of `string` specified by the `start` and `length` parameters. 参数 `string` The input string. `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` . 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 `string` is less than or equal to `start` characters long, `FALSE` will be returned. 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 a position beyond this truncation, an empty 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 "" $rest = substr("abcdef", -3, -1); // returns "de" ?>` 返回值 Returns the extracted part of string. 范例 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 achived using "curly braces" $string = 'abcdef'; echo $string{0}; // a echo $string{3}; // d echo $string{strlen($string)-1}; // f ?> 参见 strrchr() substr_replace() preg_match() trim() mb_substr() wordwrap() substr_replace trim Strings PHP Manual

substr

说明

参数

返回值

范例

参见