常见字符串和数组函数

range

<?php
// array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
foreach (range(0, 12) as $number) {
    echo $number;
}

// The step parameter was introduced in 5.0.0
// array(0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100)
foreach (range(0, 100, 10) as $number) {
    echo $number;
}

// Use of character sequences introduced in 4.1.0
// array(‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘);
foreach (range(‘a‘, ‘i‘) as $letter) {
    echo $letter;
}
// array(‘c‘, ‘b‘, ‘a‘);
foreach (range(‘c‘, ‘a‘) as $letter) {
    echo $letter;
}
?>

shuffle

<?php
$numbers = range(1, 20);
shuffle($numbers);
foreach ($numbers as $number) {
    echo "$number ";
}
?>

rand

rand() 和 mt_rand()  都是闭区间

Note: 自 PHP 4.2.0 起，不再需要用 srand() 或 mt_srand() 给随机数发生器播种 ，因为现在是由系统自动完成的

<?php
echo mt_rand() . "\n";
echo mt_rand() . "\n";

echo mt_rand(5, 15);
?>

// 计算一个随机浮点数
<?php
function randomFloat($min = 0, $max = 1) {
    return $min + mt_rand() / mt_getrandmax() * ($max - $min);
}

var_dump(randomFloat());
var_dump(randomFloat(2, 20));
?>

join

别名: implode()

# 将数组变成字符串
# 返回的是字符串
string implode ( string $glue , array $pieces )
 string implode ( array $pieces )

注意空白数组不能使用 join

<?php
$array = array(‘lastname‘, ‘email‘, ‘phone‘);
$str = join(", ", $array);

echo $str.‘‘;             // lastname,email,phone

// Empty string when using an empty array:
var_dump(join(‘hello‘, array())); // string(0) ""
?>

各种字符串分割的比较

preg_split() 函数使用了 Perl 兼容正则表达式语法，通常是比 split() 更快的替代方案。如果不需要正则表达式的威力，则使用 explode() 更快，这样就不会招致正则表达式引擎的浪费

explode

array explode ( string $delimiter, string $string [, int $limit ])

# 将字符串变成数组

<?php
// 示例 1
$pizza  = "piece1 piece2 piece3 piece4 piece5 piece6";
$pieces = explode(" ", $pizza);
echo $pieces[0]; // piece1
echo $pieces[1]; // piece2

// 示例 2
$data = "foo:*:1023:1000::/home/foo:/bin/sh";
list($user, $pass, $uid, $gid, $gecos, $home, $shell) = explode(":", $data);
echo $user; // foo
echo $pass; // *
?>

<?php
/* A string that doesn‘t contain the delimiter will simply return a one-length array of the original string. */
// 如果字符串不存在该分隔符, 那么整个字符串就会被 合并成 一个 数组
$input1 = "hello";
$input2 = "hello,there";
var_dump( explode( ‘,‘, $input1 ) );
var_dump( explode( ‘,‘, $input2 ) );
?>

<?php
$str = ‘one|two|three|four‘;

// 正数的 limit
print_r(explode(‘|‘, $str, 2));

// 负数的 limit（自 PHP 5.1 起）
print_r(explode(‘|‘, $str, -1));

// 结果
// Array
// (
//     [0] => one
//     [1] => two|three|four
// )
// Array
// (
//     [0] => one
//     [1] => two
//     [2] => three
// )
?>

split

split — 用正则表达式将字符串分割到数组中

array split (string $pattern , string $string [, int $limit ])

<?php
$passwd_line = "foo:*:1023:1000::/home/foo:/bin/sh";
list($user, $pass, $uid, $gid, $extra) = split (":", $passwd_line);
echo ‘|‘, $passwd_line, ‘|<br />‘;
echo ‘|‘, $user, ‘|‘, $pass, ‘|‘, $uid, ‘|‘, $gid, ‘|‘, $extra, ‘|<br />‘;

echo ‘<br />‘;

list($user, $pass, $uid, $gid, $extra) = split (":", $passwd_line, 5);
echo ‘|‘, $passwd_line, ‘|<br />‘;
echo ‘|‘, $user, ‘|‘, $pass, ‘|‘, $uid, ‘|‘, $gid, ‘|‘, $extra, ‘|<br />‘;


echo ‘<br />‘;

// 分隔符可以是斜线，点，或横线
$date = "04/30/1973";
list($month, $day, $year) = split (‘[/.-]‘, $date);
echo "Month: $month; Day: $day; Year: $year <br />";
?>

prep_split

preg_split — 通过一个正则表达式分隔字符串

array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )

flags
   PREG_SPLIT_NO_EMPTY         preg_split() 将进返回分隔后的非空部分
   PREG_SPLIT_DELIM_CAPTURE    用于分隔的模式中的括号表达式将被捕获并返回
   PREG_SPLIT_OFFSET_CAPTURE   对于每一个出现的匹配返回时将会附加字符串偏移量. 注意：这将会改变返回数组中的每一个元素, 使其每个元素成为一个由第 0 个元素为分隔后的子串，第 1 个元素为该子串在 subject 中的偏移量组成的数组

<?php
// 使用逗号或空格(包含" ", \r, \t, \n, \f)分隔短语
$keywords = preg_split("/[\s,]+/", "hypertext language, programming");
print_r($keywords);
// Array ( [0] => hypertext [1] => language [2] => programming )
?>

<?php
$str = ‘str ing‘;
$chars = preg_split(‘//‘, $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($chars);
// Array ( [0] => s [1] => t [2] => r [3] => [4] => i [5] => n [6] => g )
?>

<?php
$str = ‘hypertext language programming‘;
$chars = preg_split(‘/ /‘, $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($chars);

// Array (
//    [0] => Array ( [0] => hypertext [1] => 0 )
//    [1] => Array ( [0] => language [1] => 10 )
//    [2] => Array ( [0] => programming [1] => 19 )
//       )
?>

str_split

array str_split ( string $string [, int $split_length = 1 ] )

str_split — 将字符串转换为数组

<?php
$str = "Hello Friend";

$arr1 = str_split($str);
$arr2 = str_split($str, 3);

print_r($arr1);
print_r($arr2);
?>

// Array
// (
//     [0] => H
//     [1] => e
//     [2] => l
//     [3] => l
//     [4] => o
//     [5] =>
//     [6] => F
//     [7] => r
//     [8] => i
//     [9] => e
//     [10] => n
//     [11] => d
// )

// Array
// (
//     [0] => Hel
//     [1] => lo
//     [2] => Fri
//     [3] => end
// )