PHP using offsets and lengths to replace multiple strings - php

Question

I have a string like this:
'The Pear and Orange are tasty. Which one do you prefer? Pear or Orange?'
I need to replace the 'Pear' and 'Orange' strings at the end and wrap them in links. I have the following information in JSON format:
"string": "The Pear and Orange are tasty. Which one do you prefer? Pear or Orange?",
"links": {
"55": [
{
"url": "http://example.com/pear",
"name": "Pear",
"offset": 55,
"length": 4
}
],
"63": [
{
"url": "http://example.com/orange",
"name": "Orange",
"offset": 63,
"length": 6
}
]
I want to use the offset and length to replace the strings rather than relying on the names, because the main string may contain multiple occurrences of the words.
What I've tried:
1) I've tried using a foreach loop to loop through the links in the JSON and replace them using substr_replace but after the first loop the offset is then not accurate as I've replaced the first string with a link, which increases the length of the original string by 20-30 characters.
2) I then tried passing replace, offset and length arrays to substr_replace to try to replace all the strings in one go, but that didn't work as the original string isn't in an array format, it's just a plain string.
Does anyone have any ideas or pointers for me? Any help would be hugely appreciated as I'm pulling my hair out. It seems so simple yet I can't quite get it!
Many thanks,
John

Answer 1

Your first instinct was right. The only change you need to make is to make the for loop start with the last entry and loop backward, in stead of the other way around. This will work because the offset of a word only changes if you change something that comes before that word in the string.
for($i = count($links)-1; $i >= 0; $i--) {
str_replace( ... );
}
The above approach requires that the links are sorted according to their offset, however, with the highest offset coming last in the array. If the links aren't sorted, you will have to do that first. But if you need to sort the array, you might as well sort them so that the highest offset comes first and loop through the array the normal way around.
For example:
$links = array(
array( 'name' => 'Pear', 'offset' => 55 ),
array( 'name' => 'Orange', 'offset' => 63 ),
array( 'name' => 'LAST', 'offset' => 0 ),
array( 'name' => 'MIDDLE', 'offset' => 60 ),
array( 'name' => 'FIRST', 'offset' => 1000)
);
function mySort($a, $b) {
return $b['offset'] - $a['offset']; // Sorts elements with higher offset first
}
usort($links, 'mySort');