Create all possible sentence from an Array of words - php

Question

From this Array of Words
$words = ['THIS', 'IS', 'AN', 'EXAMPLE'];
I want to make Sentences like the following:
$sentences = [
'THIS IS AN EXAMPLE',
'THIS IS AN',
'THIS IS',
'THIS'
];
Also i would like to know how to reverse the ORDER of it,
Like to start from THIS to EXAMPLE like 'THIS IS AN EXAMPLE'
Or to start from EXAMPLE to THIS like 'EXAMPLE AN IS THIS'
or getting both from Forward to Backward and from Backward to Forward so i get
$sentences = [
'THIS IS AN EXAMPLE',
'THIS IS AN',
'THIS IS',
'THIS',
`EXAMPLE AN IS THIS`,
`EXAMPLE AN IS`,
`EXAMPLE AN`,
`EXAMPLE`
];
What I've tried was
$sentences = [];
$words = ['THIS', 'IS', 'AN', 'EXAMPLE'];
$wordscount = count($words);
$i = 1;
while ($i < $wordscount) {
$newword = '';
foreach ($words as $word) {
$newword .= "$word ";
}
while (in_array($newword, $sentences)) {
$newword = explode(' ', $newword);
$newword = array_pop($newword);
$newword = implode(' ', $newword);
echo "$newword <br>";
}
$sentences[] = $newword;
$i++;
}
print_r($sentences);
and it is incomplete Because when i load the page the Web Browser and FastCGI CPU Usage Jumps to 50% for each one And page shows me Memory Usage Problem.

Answer 1

This is how I would do it:
Create a loop which will iterate the total amount of items in the array.
Reduce the array by the iteration value and implode it into a return
array.
Then do the same again but simply with a reversed array and merge them both.
For example:
<?php
function join_words($words) {
$return = [];
for ($i=0; $i < count($words); $i++) {
$return[] = implode(' ', array_slice($words, 0, $i+1));
}
return $return;
}
$words = ['THIS', 'IS', 'AN', 'EXAMPLE'];
$result = [];
$result = array_merge($result, join_words($words));
$result = array_merge($result, join_words(array_reverse($words)));
print_r($result);
https://3v4l.org/vG7tj
Result:
Array
(
[0] => THIS
[1] => THIS IS
[2] => THIS IS AN
[3] => THIS IS AN EXAMPLE
[4] => EXAMPLE
[5] => EXAMPLE AN
[6] => EXAMPLE AN IS
[7] => EXAMPLE AN IS THIS
)
If you want the exact output as shown, you should reverse the array before merging it.
$result = [];
$result = array_merge($result, array_reverse(join_words($words)));
$result = array_merge($result, array_reverse(join_words(array_reverse($words))));
https://3v4l.org/R4LDo
Result:
Array
(
[0] => THIS IS AN EXAMPLE
[1] => THIS IS AN
[2] => THIS IS
[3] => THIS
[4] => EXAMPLE AN IS THIS
[5] => EXAMPLE AN IS
[6] => EXAMPLE AN
[7] => EXAMPLE
)