Multiple String Replace Based on Index

Question

I need to replace multiple sections of a string based on their indices.

$string  = '01234567890123456789';

$replacements = array(
    array(3, 2, 'test'),
    array(8, 2, 'haha')
);

$expected_result = '012test567haha0123456789';

Indices in $replacements are expected not to have overlaps.

I have been trying to write my own solution, split the original array into multiple pieces based on sections which needs to be replaced or not, and finally combine them:

echo str_replace_with_indices($string, $replacements);
// outputs the expected result '012test567haha0123456789'

function str_replace_with_indices ($string, $replacements) {
    $string_chars = str_split($string);

    $string_sections = array();
    $replacing = false;
    $section = 0;
    foreach($string_chars as $char_idx => $char) {
        if ($replacing != (($r_idx = replacing($replacements, $char_idx)) !== false)) {
            $replacing = !$replacing;
            $section++;
        }
        $string_sections[$section] = $string_sections[$section] ? $string_sections[$section] : array();
        $string_sections[$section]['original'] .= $char;
        if ($replacing) $string_sections[$section]['new'] = $replacements[$r_idx][2];
    }

    $string_result = '';
    foreach($string_sections as $s) {
        $string_result .= ($s['new']) ? $s['new'] : $s['original'];
    }

    return $string_result; 
}

function replacing($replacements, $idx) {
   foreach($replacements as $r_idx => $r) {
       if ($idx >= $r[0] && $idx < $r[0]+$r[1]) {
           return $r_idx;
       }
   }
   return false;
}

Is there any more effective way to achieve the same result?

The above solution doesn't look elegant and feels quite long for string replacement.

Ramz · Accepted Answer · 2013-11-22 10:18:10Z

2

Use this

$str = '01234567890123456789';
$rep = array(array(3,3,'test'), array(8,2,'haha'));
$index = 0;
$ctr = 0;
$index_strlen = 0;
foreach($rep as $s)
{
   $index = $s[0]+$index_strlen;

   $str = substr_replace($str, $s[2], $index, $s[1]);

   $index_strlen += strlen($s[2]) - $s[1];
}
echo $str;

edited Nov 22, 2013 at 10:18

answered Nov 22, 2013 at 6:16

Ramz

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6 Comments

Irwan Over a year ago

$rep is missing length of characters needs to be replaced. This only replaces 1 character for each $rep.

Ramz Over a year ago

you set $repeat to number of repeats for each char

Irwan Over a year ago

$repeat = 1; gets me 12test4567haha9123456789. $repeat = 2; gets me 12test4567haha912test4567haha9. And the number of characters needs to be replaced can be different for each $rep, not fixed.

Irwan Over a year ago

hmm.. to be clear, '3' and '8' in $rep should be indices in $str, not substring to replace.

Irwan Over a year ago

It is not. array(3, 2, 'test') means: starting from the third index as many as two characters, replace with 'test' (four characters). In this case, strlen() will increase by 2.

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