PHP case-insensitive array search functions [duplicate]

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Possible Duplicate:

PHP case-insensitive in_array function

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('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. Because it is case sensitive.

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If you want to apply strtolower on each element of the array, use array_map:

in_array(strtolower('ONE'), array_map('strtolower', $a));