How to check if array elements exist in a string

Question

I have a list of words in an array. What is the fastest way to check if any of these words exist in an string?

Currently, I am checking the existence of array elements one by one through a foreach loop by stripos. I am curious if there is a faster method, like what we do for str_replace using an array.

do you only want to know if there is a match or do you want to know what the match is (or how often it occurs)? — MonkeyMonkey
– MonkeyMonkey, Commented May 21, 2012 at 22:36
@MonkeyMonkey I just want to check if they exist; no matter where and how many times. — Googlebot
– Googlebot, Commented May 21, 2012 at 22:37

Community · Accepted Answer · 2017-05-23 11:56:29Z

2

Regarding to your additional comment you could explode your string into single words using explode() or preg_split() and then check this array against the needles-array using array_intersect(). So all the work is done only once.

<?php
$haystack = "Hello Houston, we have a problem";
$haystacks = preg_split("/\b/", $haystack);
$needles = array("Chicago", "New York", "Houston");
$intersect = array_intersect($haystacks, $needles);
$count = count($intersect);

var_dump($count, $intersect);

I could imagine that array_intersect() is pretty fast. But it depends what you really want (matching words, matching fragments, ..)

edited May 23, 2017 at 11:56

CommunityBot

11 silver badge

answered May 21, 2012 at 22:54

MonkeyMonkey

8361 gold badge6 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

dynamic · Accepted Answer · 2012-05-21 22:38:41Z

1

my personal function:

function wordsFound($haystack,$needles) {
    return preg_match('/\b('.implode('|',$needles).')\b/i',$haystack);      
}

//> Usage:
if (wordsFound('string string string',array('words')))

Notice if you work with UTF-8 exotic strings you need to change \b with teh corrispondent of utf-8 preg word boundary

Notice2: be sure to enter only a-z0-9 chars in $needles (thanks to MonkeyMonkey) otherwise you need to preg_quote it before

Notice3: this function is case insensitve thanks to i modifier

edited May 21, 2012 at 22:38

answered May 21, 2012 at 22:33

dynamic

48.2k56 gold badges163 silver badges236 bronze badges

4 Comments

Googlebot Over a year ago

since my concern is about performance; is preg_match faster than foreach loop?

dynamic Over a year ago

@Ali: yes for this case. it may depends on the $needles size tho

MonkeyMonkey Over a year ago

you should use preg_quote() before that, otherwise there's the possibility of a regex-injection

dynamic Over a year ago

@MonkeyMonkey: added a notice

CodeZombie · Accepted Answer · 2012-05-21 22:37:49Z

0

In general regular expressions are slower compared to basic string functions like str_ipos(). But I think it really depends on the situation. If you really need the maximum performance, I suggest making some tests with real-world data.

answered May 21, 2012 at 22:37

CodeZombie

5,3753 gold badges32 silver badges37 bronze badges

2 Comments

Googlebot Over a year ago

stripos is very fast. It is not matter of stripos; the problem is that we need to perform stripos MANY times through the foreach loop.

CodeZombie Over a year ago

@Ali: Thanks, I know. As I said you should really compare both approaches using real-world data.

Collectives™ on Stack Overflow

How to check if array elements exist in a string

3 Answers 3

Comments

4 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

4 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related