CODEWITHSUNDEEP
phpstring
Kanishka Panamaldeniya
Kanishka Panamaldeniya

Reputation: 17586

Easiest way to replace all characters in even positions in a string.

$str = "helloworld";

I want to create string 

$newStr = "h l o o l ";

So as you can see i want to replace the chars in positions , 2,4,6,8,10 (assuming first character is in position 1).

I can do something like this 

<?php

$str = 'helloworld';
$newStr = '';
for($i=0;$i<strlen($str);$i++) {
    if($i%2==0) {
        $newStr .=  $str[$i];
    } else {
           $newStr .= ' ';
    }
}

echo $newStr;

?>

But is there a more easier way or a one line in built function available to do this task .

Thanks in advance .

Upvotes: 9

Views: 3006

Answers (5)

mickmackusa
mickmackusa

Reputation: 48001

I think a regex technique will be cleanest, but I'll show a couple more for contrast.

  1. preg_replace() allows the most concise, single-function call solution. The pattern employs the \K metacharacter to eliminate the need for a capture group (capture groups cost extra "steps", so avoid them when sensible). \K means forget any previously matched characters and restart the "fullstring match" from this point in the string. In other words, it consumes the odd characters (by the OP's definition of "odd|even") then discards them, then matches whatever single-byte chatacter comes next.

  2. Most laborious of my set of techniques, the multi-functional approach splits the input string into an array of strings with at most 2-characters, then if the substring has a second character, it is replaced with a space before being reattached to reconstructed string.

  3. A for loop is likely to be the best performing, but isn't the type of scripting that is instantly readable (that said, some people find regex hard to read). Note, it is important to not call strlen() on each iteration. To avoid this, cache the length before the loop or in the first parameter of the loop.

Code: (Demo)

$str = "helloworld";

echo preg_replace('~.\K.~', ' ', $str);

echo "\n---\n";

echo array_reduce(str_split($str, 2), function($carry, $item) {
         return $carry . $item[0] . (isset($item[1]) ? ' ' : '');
     });

echo "\n---\n";

for ($offset = 1, $length = strlen($str); $offset < $length; $offset += 2) {
    $str[$offset] = ' ';
}
echo $str;

Output:

h l o o l 
---
h l o o l 
---
h l o o l

Upvotes: 0

Blinkydamo
Blinkydamo

Reputation: 1584

Try this, a little shorter then yours but is a one-liner as you asked.

$str    = 'helloworld';
$newStr = '';
for( $i = 0; $i < strlen( $str ); $i++) { $newStr .= ( ( $i % 2 ) == 0 ? $str[ $i ] : ' ' ); }
echo $newStr;

Upvotes: 2

Ortho
Ortho

Reputation: 919

Firstly you can increase your counter by two, so you don't have to check if it's odd. Secondly because strings are treated like char arrays you can access a char at position $i with $str[$i].

$str = "Hello World";
$newStr = $str;
for($i = 1; $i < strlen($str); $i += 2) {
  $newStr[$i] = ' ';
}
echo $newStr;

Have a Nice day.

[Edit] Thanks ringo for the hint.

Upvotes: 3

Mihai
Mihai

Reputation: 26784

Similar but using generator

$str = 'helloworld';
$newstr ='';
foreach(range($str, strlen($str)-1, 2) as $i){
$newstr.=$str[$i].' ';
}

Upvotes: 1

Ruslan Osmanov
Ruslan Osmanov

Reputation: 21502

It is easily done with a regular expression:

echo preg_replace('/(.)./', '$1 ', $str);

The dot matches a character. Every second character is replaced with a space.

Upvotes: 10

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