String between string with array in PHP, array order ISSUE - php

Question

I'm facing an issue with a function that gets a string between two other strings.
function string_between($str, $starting_word, $ending_word) {
$subtring_start = strpos($str, $starting_word);
$subtring_start += strlen($starting_word);
foreach ($ending_word as $a){
$size = strpos($str, $a, $subtring_start) - $subtring_start;
}
return substr($str, $subtring_start, $size);
}
The issue is that the function searches for the first ending_word in the array.
An example will be easier to understand:
$array_a = ['the', 'amen']; // Starting strings
$array_b = [',', '.']; // Ending strings
$str = "Hello, the world. Then, it is over.";
Expected result:
"the world."
Current result:
"the world. Then,"
The function will think that the ending_word is "," because it is the first element met in the array_b. However, the text encounters first the '.' after the "the" starting word.
How can I make sure the function goes through the text and stops at the first element in the $str present in the array_b, whatever the position in the array?
Any idea?

Answer 1

Basically, you need to break outside of your foreach loop when $size > 0
That way it stops looping through your array when it finds the 1st occurrence. Here is the more complete code with other fixes:
function stringBetween($string, $startingWords, $endingWords) {
foreach ($startingWords as $startingWord) {
$subtringStart = strpos($string, $startingWord);
if ($subtringStart > 0) {
foreach ($endingWords as $endingWord){
$size = strpos($string, $endingWord, $subtringStart) - $subtringStart + strlen($endingWord);
if ($size > 0) {
break;
}
}
if ($size > 0) {
return substr($string, $subtringStart, $size);
}
}
}
return null;
}
$startArr = array('the', 'amen'); // Starting strings
$endArr = array('.', ','); // Ending strings
$str = "Hello, the world. Then, it is over.";
echo stringBetween($str, $startArr, $endArr); // the world.

Answer 2

This type of problems are best solved by PCRE regexes, only couple of lines needed in function :
function string_between($str, $starts, $ends) {
preg_match("/(?:{$starts}).*?(?:{$ends})/mi", $str, $m);
return $m[0];
}
Then calling like this :
echo string_between("Hello, the world. Then, it is over.", 'the|amen', ',|\.');
Produces : the world.
The trick,- search to the nearest matching ending symbol is done with regex non-greedy seach, indicated by question symbol in pattern .*?. You can even extend this function to accept arrays as starting/ending symbols, just that case modify function (possibly with implode('|',$arr)) for concatenating symbols into regex grouping formula.

Answer 3

Edited version
This works now. Iterate over your teststrings from first array looking for position of occurance from teststring. If found one then search for the second teststring at startposition from end of first string.
To get the shortest hit I store the position from the second and take the minimum.
You can try it at http://sandbox.onlinephpfunctions.com/code/0f1e5c97da62b4daaf0e49f52271fe288d1cacbb
$array_a =array('the','amen');
$array_b =array(',','.', '#');
$str = "Hello, the world. Then, it is over.";
function earchString($str, $array_a, $array_b) {
forEach($array_a as $test) {
$pos = strpos($str, $test);
if ($pos===false) continue;
$found = [];
forEach($array_b as $test2) {
$posStart = $pos+strlen($test);
$pos2 = strpos($str, $test2, $posStart);
$found[] = ($pos2!==false) ? $pos2 : INF;
}
$min = min($found);
if ($min !== INF)
return substr($str,$pos,$min-$pos) .$str[$min];
}
return '';
}
echo earchString($str, $array_a, $array_b);