Get all the palindromes in a string - php

Question

I was asked to write a program in php where all the occurrences of palindromes in a given string need to be printed.
Example: For the string I O M K I L O L I K T C J I O P L L P O
The answer would be:
O P L L P O and
K I L O L I K
While doing this it should kept in mind that every palindrome that is more than 3 characters in length can be broken down into more palindromes but you just need to print out the longest size possible for each set (so, for the example string, you SHOULD NOT print LOL, LL , PLLP and ILOLI)
I tried it but could only manage to do this:
$data = 'I O M K I L O L I K T C J I O P L L P O';
$data = str_replace(' ', '', $data);
$palindromes = [];
for($i=0; $i<strlen($data); $i++ ) {
for($j=3; $j<=(strlen($data)-$i); $j++){
$word = substr($data, $i, $j);
$reverse_word = strrev($word);
if($word == $reverse_word){
print "Word: ".$word."<br/>";
}
}
}
Which gives me the following output:
Word: KILOLIK
Word: ILOLI
Word: LOL
Word: OPLLPO
Word: PLLP
Which is not the expected ouput. What should I to get rid of the strings like ILOLI, LOL PLLP because I am expected to get the longest palindrome.

Answer 1

According your example, you mention the answer would be O P L L P O (six characters long) and K I L O L I K (seven characters long), but later you imply only the longest palindrome should be returned?
Assuming you mean the later case, you can first assign all the palindromes to array and then sort the array, like this:
function str_length_sort($first, $second) {
return strlen($second) - strlen($first);
}
$data = 'I O M K I L O L I K T C J I O P L L P O';
$data = str_replace(' ', '', $data);
$palindromes = [];
for($i=0; $i<strlen($data); $i++ ) {
for($j=3; $j<=(strlen($data)-$i); $j++){
$word = substr($data, $i, $j);
$reverse_word = strrev($word);
if($word == $reverse_word){
$palindromes[] = $word;
}
}
}
usort($palindromes, 'str_length_sort');
$max = strlen($palindromes[0]);
foreach ($palindromes as $p) {
$length = strlen($p);
if ($length >= $max) {
echo $p;
}
}
Hope this helps.