Search files question

How can I search for file with any of the key search word in string.

Currently example if my key search is number 3 it will find files that start with the number 3.jpg

How ever for example I would like to be able to find files that have 123.jpg also. I need to be able to search for letters and numbers.

PHP Code:

if (null !==($this->input->get('directory'))) {
$directory = $this->security->xss_clean(DIR_IMAGE .'catalog/'. $this->input->get('directory', TRUE));
} else {
    $directory = $this->security->xss_clean(DIR_IMAGE .'catalog');
}

if ($this->input->post('search')) {
    $filter_name = $this->input->post('search', TRUE);
} else {
    $filter_name = null;
}

 // Get directories
$directories = glob($directory . '/' . $filter_name . '*', GLOB_ONLYDIR);

if (!$directories) {
    $directories = array();
}

// Get files
$files = glob($directory . '/' . $filter_name . '*.{jpg,jpeg,png,gif,JPG,JPEG,PNG,GIF}', GLOB_BRACE);

natsort($files);

if (!$files) {
      $files = array();
}

// Other Code 


There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!