PHP - 迭代字符串字符

PHP - iterate on string characters

提问by jon_darkstar

Is there a nice way to iterate on the characters of a string? I'd like to be able to do foreach, array_map, array_walk, array_filteretc. on the characters of a string.

有没有一种很好的方法来迭代字符串的字符？我希望能够做到foreach，array_map，array_walk，array_filter在字符串中的字符等。

Type casting/juggling didnt get me anywhere (put the whole string as one element of array), and the best solution I've found is simply using a for loop to construct the array. It feels like there should be something better. I mean, if you can index on it shouldn't you be able to iterate as well?

类型转换/杂耍并没有让我在任何地方（将整个字符串作为数组的一个元素），我发现的最佳解决方案只是使用 for 循环来构造数组。感觉应该有更好的东西。我的意思是，如果你可以索引它，你不应该也可以迭代吗？

This is the best I've got

这是我最好的

function stringToArray($s)
{
    $r = array();
    for($i=0; $i<strlen($s); $i++) 
         $r[$i] = $s[$i];
    return $r;
}

$s1 = "textasstringwoohoo";
$arr = stringToArray($s1); //$arr now has character array

$ascval = array_map('ord', $arr);  //so i can do stuff like this
$foreach ($arr as $curChar) {....}
$evenAsciiOnly = array_filter( function($x) {return ord($x) % 2 === 0;}, $arr);

Is there either:

是否有：

A) A way to make the string iterable
B) A better way to build the character array from the string (and if so, how about the other direction?)

A）使字符串可迭代的方法
B）从字符串构建字符数组的更好方法（如果是，另一个方向怎么样？）

I feel like im missing something obvious here.

我觉得我在这里遗漏了一些明显的东西。

回答by SeaBrightSystems

Step 1:convert the string to an array using the str_splitfunction

步骤 1：使用str_split函数将字符串转换为数组

$array = str_split($your_string);

$array = str_split($your_string);

Step 2:loop through the newly created array

第 2 步：遍历新创建的数组

foreach ($array as $char) {
 echo $char;
}

You can check the PHP docs for more information: str_split

您可以查看 PHP 文档以获取更多信息： str_split

回答by Owen

Iterate string:

迭代字符串：

for ($i = 0; $i < strlen($str); $i++){
    echo $str[$i];
}

回答by Dawid Ohia

If your strings are in Unicode you should use preg_splitwith /umodifier

如果你的字符串是用Unicode，你应该使用preg_split与/u修改

From comments in php documentation:

来自 php 文档中的评论：

function mb_str_split( $string ) { 
    # Split at all position not after the start: ^ 
    # and not before the end: $ 
    return preg_split('/(?<!^)(?!$)/u', $string ); 
} 

回答by Moritur

You can also just access $s1 like an array, if you only need to access it:

如果您只需要访问它，您也可以像访问数组一样访问 $s1：

$s1 = "hello world";
echo $s1[0]; // -> h

回答by Dairy Window

Expanded from @SeaBrightSystems answer, you could try this:

从@SeaBrightSystems 答案扩展，你可以试试这个：

$s1 = "textasstringwoohoo";
$arr = str_split($s1); //$arr now has character array

回答by AmirHossein

For those who are looking for the fastest way to iterate over strings in php, Ive prepared a benchmark testing.
The first method in which you access string characters directly by specifying its position in brackets and treating string like an array:

对于那些正在寻找在 php 中迭代字符串的最快方法的人，我准备了一个基准测试。
第一种方法是通过在括号中指定其位置并将字符串视为数组来直接访问字符串字符：

$string = "a sample string for testing";
$char = $string[4] // equals to m

I myself thought the latter is the fastest method, but I was wrong.
As with the second method (which is used in the accepted answer):

我自己认为后者是最快的方法，但我错了。
与第二种方法（在接受的答案中使用）一样：

$string = "a sample string for testing";
$string = str_split($string);
$char = $string[4] // equals to m

This method is going to be faster cause we are using a realarray and not assuming one to be an array.

这种方法会更快，因为我们使用的是一个真正的数组，而不是假设一个数组是一个数组。

Calling the last line of each of the above methods for 1000000times lead to these benchmarking results:

1000000多次调用上述每个方法的最后一行会导致这些基准测试结果：

Using string[i]
0.24960017204285 Seconds

使用字符串[i]
0.24960017204285 Seconds

Using str_split
0.18720006942749 Seconds

使用 str_split
0.18720006942749 Seconds

Which means the second method is way faster.

这意味着第二种方法要快得多。

回答by Ash

Hmm... There's no need to complicate things. The basics work great always.

嗯……没必要把事情复杂化。基础工作总是很好。

    $string = 'abcdef';
    $len = strlen( $string );
    $x = 0;

Forward Direction:

前进方向：

while ( $len > $x ) echo $string[ $x++ ];

Outputs: abcdef

输出： abcdef

Reverse Direction:

反向：

while ( $len ) echo $string[ --$len ];

Outputs: fedcba

输出： fedcba

回答by masakielastic

// Unicode Codepoint Escape Syntax in PHP 7.0
$str = "cat!\u{1F431}";

// IIFE (Immediately Invoked Function Expression) in PHP 7.0
$gen = (function(string $str) {
    for ($i = 0, $len = mb_strlen($str); $i < $len; ++$i) {
        yield mb_substr($str, $i, 1);
    }
})($str);

var_dump(
    true === $gen instanceof Traversable,
    // PHP 7.1
    true === is_iterable($gen)
);

foreach ($gen as $char) {
    echo $char, PHP_EOL;
}

回答by Accountant ?

Most of the answers forgot about non English characters !!!

大多数答案都忘记了非英文字符！！！

strlencounts BYTES, not characters, that is why it is and it's sibling functions works fine with English characters, because English characters are stored in 1 byte in both UTF-8 and ASCII encodings, you need to use the multibyte string functionsmb_*

strlen计数字节，而不是字符，这就是为什么它是，它的兄弟函数适用于英文字符，因为英文字符在 UTF-8 和 ASCII 编码中都存储在 1 个字节中，您需要使用多字节字符串函数mb_*

This will work with anycharacter encoded in UTF-8

这将适用于任何编码的字符UTF-8

// 8 characters in 12 bytes
$string = "abcd????";

$charsCount = mb_strlen($string, 'UTF-8');
for($i = 0; $i < $charsCount; $i++){
    $char = mb_substr($string, $i, 1, 'UTF-8');
    var_dump($char);
}

This outputs

这输出

string(1) "a"
string(1) "b"
string(1) "c"
string(1) "d"
string(2) "?"
string(2) "?"
string(2) "?"
string(2) "?"