PHP - iterate on string characters

问题

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_filter etc. on the characters of a string.

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?

This is the best I've got

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:

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?)

I feel like im missing something obvious here.

回答1:

Step 1: convert the string to an array using the str_split function

$array = str_split($your_string);

Step 2: loop through the newly created array

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

You can check the PHP docs for more information: str_split

回答2:

Iterate string:

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

回答3:

If your strings are in Unicode you should use preg_split with /u modifier

From comments in php documentation:

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4:

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

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

回答5:

Expanded from @SeaBrightSystems answer, you could try this:

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

回答6:

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:

$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):

$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 real array and not assuming one to be an array.

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

Using string[i]
0.24960017204285 Seconds

Using str_split
0.18720006942749 Seconds

Which means the second method is way faster.

回答7:

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

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

Forward Direction:

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

Outputs: abcdef

Reverse Direction:

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

Outputs: fedcba

回答8:

// 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9:

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

strlen counts 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 functions mb_*

This will work with any character encoded in UTF-8

// 8 characters in 12 bytes
$string = "abcdأبتث";

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

This outputs

string(1) "a"
string(1) "b"
string(1) "c"
string(1) "d"
string(2) "أ"
string(2) "ب"
string(2) "ت"
string(2) "ث"

来源：https://stackoverflow.com/questions/4601032/php-iterate-on-string-characters

标签

php

string

character-arrays