Search for PHP array element containing string

To find values that match your search criteria, you can use array_filter function:

$example = array('An example','Another example','Last example');
$searchword = 'last';
$matches = array_filter($example, function($var) use ($searchword) { return preg_match("/\b$searchword\b/i", $var); });

Now $matches array will contain only elements from your original array that contain word last (case-insensitive).

If you need to find keys of the values that match the criteria, then you need to loop over the array:

$example = array('An example','Another example','One Example','Last example');
$searchword = 'last';
$matches = array();
foreach($example as $k=>$v) {
    if(preg_match("/\b$searchword\b/i", $v)) {
        $matches[$k] = $v;
    }
}

Now array $matches contains key-value pairs from the original array where values contain (case- insensitive) word last.

function customSearch($keyword, $arrayToSearch){
    foreach($arrayToSearch as $key => $arrayItem){
        if( stristr( $arrayItem, $keyword ) ){
            return $key;
        }
    }
}