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up vote 33 down vote favorite
8

Is it possible to do case-insensitive comparison when using the in_array function?

So with a source array like this:

$a= array(
 'one',
 'two',
 'three',
 'four'
);

The following lookups would all return true:

in_array('one', $a);
in_array('two', $a);
in_array('ONE', $a);
in_array('fOUr', $a);

What function or set of functions would do the same? I don't think in_array itself can do this.

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4 Answers

up vote 31 down vote accepted

you can use preg_grep():

$a= array(
 'one',
 'two',
 'three',
 'four'
);

print_r( preg_grep( "/ONe/i" , $a ) );
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+1 good suggestion –  cletus Jan 30 '10 at 2:10
12  
using regular expressions isn't a good solution, because it can be slow... maybe array_map is faster –  Philipp Oppermann Feb 2 '12 at 15:05
2  
To make it a drop-in replacement for in_array, returning a bool, it becomes: count(preg_grep('/^'.preg_quote($needle).'/$',$a)>0). Not so elegant, then. (Notice the ^ and $ characters are required, unless partial matching is desired.) However if you actually want the matching entries returned, I like this solution. –  Darren Cook Sep 14 '12 at 6:57
1  
The last comment contains a syntax error: /$ should be $/ instead. –  gogowitsch Dec 12 '12 at 15:01
1  
@DarrenCook as far as i know a bool cast would also work (bool)preg_grep('/^'.preg_quote($needle).'$/',$a), as an empty array would cast to false –  arraintxo Apr 9 '13 at 12:20
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up vote 50 down vote

The obvious thing to do is just convert the search term to lowercase:

if (in_array(strtolower($word), $a) { 
  ...

of course if there are uppercase letters in the array you'll need to do this first:

$search_array = array_map('strtolower', $a);

and search that. There's no point in doing strtolower on the whole array with every search.

Searching arrays however is linear. If you have a large array or you're going to do this a lot, it would be better to put the search terms in key of the array as this will be much faster access:

$search_array = array_combine(array_map('strtolower', $a), $a);

then

if ($search_array[strtolower($word)]) { 
  ...

The only issue here is that array keys must be unique so if you have a collision (eg "One" and "one") you will lose all but one.

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up vote 26 down vote 
function in_arrayi($needle, $haystack) {
    return in_array(strtolower($needle), array_map('strtolower', $haystack));
}

From Documenation

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You should blockquote code (or anything really) you get from somewhere else. –  cletus Jan 30 '10 at 2:05
6  
I figured that the 'From Documentation' with a link would be sufficient... –  Chacha102 Jan 30 '10 at 2:05
 
Just to be clear. It's not a criticism. Just a suggestion (and only my opinion, nothing official). :) At least if I copy a code snippet from a page I'll block quote it. –  cletus Jan 30 '10 at 2:07
 
Plus, using a code block better describes it, as it is 'code'. Block quoting it does not allow for it to be properly formatted. –  Chacha102 Jan 30 '10 at 2:08
 
You can put a code block inside a block quote. –  cletus Jan 30 '10 at 2:08
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up vote 15 down vote 
function in_arrayi($needle, $haystack) {
    return in_array(strtolower($needle), array_map('strtolower', $haystack));
}

Source: php.net in_array manual page.

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If you know what is in the array, you can leave out the array_map; but this is a good example. –  Don Jan 30 '10 at 1:58
1  
Who downvoted a perfectly good example and solution? –  Doug Neiner Jan 30 '10 at 2:00
 
I did actually. Because mapping the array on every call is, well, ludicrous. –  cletus Jan 30 '10 at 2:02
 
Also, assuming (like Chacha) this comes direct from the docs, it's better to block quote it. –  cletus Jan 30 '10 at 2:05
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