Array A:
486 987
Array B:
247-16-02-2009 486-16-02-2009 562-16-02-2009 1257-16-02-2009 486-16-02-2009
I want to search and list all Array A elements that matches in Array B. for example: 486-16-02-2009 (twice).
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4 Answers
You can use a regex by imploding $arrayA into a pattern. This will find $arrayA items anywhere in $arrayB items:
$pattern = implode("|", $arrayA);
$result = preg_grep("/$pattern/", $arrayB);
To match only at the start of $arrayB items use the ^ anchor "/^$pattern/".
You may want to run $arrayA elements through preg_quote() if there may be special pattern characters there.
6 Comments
Lando
Interesting approach!
Spencer D
Definitely an interesting and unique approach, so +1 for that. Overall, I like this approach; however, how would this compare to looping in terms of processing time and overhead? The RegEx engine requires a decent amount of overhead (memory) and generally has a slower processing time for such simple tasks like this. In the OP's example, the processing time and overhead would be miniscule/negligible, but the use of RegEx may have adverse effects on scalability. Nonetheless, this answer deserves an upvote because it is so short and unique from all other answers.
Shehryar Khalid
It returns empty array: /*$pattern = preg_quote(implode("|", $arrayA), "/"); $result = preg_grep("/^$pattern/", $arrayB); while pipe sign "|" returns all elements of $arrayB. but it doesn't return the match!
AbraCadaver
Edited. preg_quote was escaping the |
Shehryar Khalid
Thank you, it worked. I have a basic question in mind, how preg_grep function match "/$pattern/" in the source string "n40000|315758|465213|"? what would be the pattern? if I implode Array A string with asterisk "*". Thank you for your kind help Sir.
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You could do something like this, however it's probably not as good as using php built-ins like array-intersect because we're entering loop-hell. If either array gets too big your script will slow to a crawl.
foreach ($arrB as $values) {
foreach ($arrA as $compare) {
if (substr($values, 0, strlen($compare)) == $compare) {
//do stuff
}
}
}
2 Comments
Shehryar Khalid
Its only pull the first part of the string i.e. 486. I need complete string like: 486-16-02-2009
Shehryar Khalid
Any other way to improve the processing time?
You must walk the two arrays searching for each case:
Working example: http://ideone.com/pDCZ1R
<?php
$needle = [486, 987];
$haystack = ["247-16-02-2009", "486-16-02-2009", "562-16-02-2009", "1257-16-02-2009", "486-16-02-2009"];
$result = array_filter($haystack, function($item) use ($needle){
foreach($needle as $v){
if(strpos($item, strval($v)) !== false){
return true;
}
}
return false;
});
print_r($result);
Comments
Somewhat similar to two of the other answers, but this would be my approach:
$matches = array(); // We'll store the matches in this array
// Loop through all values we are searching for
foreach($arrayA as $needle){
// Loop through all values we are looking within
foreach($arrayB as $haystack){
if(strpos($needle, $haystack) !== false){
// We found a match.
// Let's make sure we do not add the match to the array twice (de-duplication):
if(!in_array($haystack, $needle, true)){
// This match does not already exist in our array of matches
// Push it into the matches array
array_push($matches, $haystack);
}
}
}
}
Note: This solution uses in_array() to prevent match duplication. If you would like matches that match more than one value to show up more than once, then simply remove the if-statement that has !in_array(...) as its conditional.