Multiple String Replace Based on Index - php

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.

Answer 1

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;