Question 161415 in PHP Question posted in
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Can PHP prepend a string to each character of another string?

I have the following code:

$target = "abcwa";

for($w = 0; $w <=strlen($target)-1; $w++)
{
  $str = str_split($target[$w],1); //a
  $str_ = $str[$w];
            
  echo "w:";$w;
  echo $str_;
}// end for w

It is printing:

w:a
Warning: Undefined array key 1 in /in/n705C on line 8
w:
Warning: Undefined array key 2 in /in/n705C on line 8
w:
Warning: Undefined array key 3 in /in/n705C on line 8
w:
Warning: Undefined array key 4 in /in/n705C on line 8
w:

Line 8 is $str_ = $str[$w];.

However the goal is to print: w:aw:bw:cw:ww:a

What is wrong?

Tags:

2

Answers


  1. 0

    Your loop has:

    $w <= strlen($target) - 1

    This is more commonly done with:

    $w < strlen($target)

    But you don’t need any loops at all here. Start by splitting the string into an array of individual letters:

    str_split($target);

    This gives you: ['a', 'b', 'c', 'w', 'a']

    Then re-combine that array into a string, but with "w:" between each element:

    echo implode('w:', str_split($target));

    This gives you:

    aw:bw:cw:ww:a

    Then just tack on your leading "w:":

    echo 'w:' . implode('w:', str_split($target));

    Which yields:

    w:aw:bw:cw:ww:a

    Alternatively, you could add a space to the start of your string, so that the split has one extra character at the start, for the implode to act on:

    echo implode('w:', str_split(' ' . $target));

    Which yields:

     w:aw:bw:cw:ww:a

    (Note there’s an extra space in the output in this case, if that matters.)

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  2. 0

    I would abandon your original code because it is verbose and has multiple failing components.

    Instead, just use regex to insert your desired string before each character.

    Codes: (Demo)

    echo preg_replace('/./', 'w:$0', $target);

    Or

    echo preg_replace('/(?=.)/', 'w:', $target);
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