grep.php

<?php
/**
 * Search a block of text for a given text string
 * 
 * @param   string        $pattern
 *  A regexp to match against
 * @param   string|array  $input
 *  A string or array (can't handle recursiveness) to search
 * @param   int           $context
 *  Returns x number of lines surrounding the hit
 * @return  string        $output
 */
function grep($pattern, $input, $context = 0) {
  if (is_string($input)) {
    $input = explode("\n", $input);
  }

  if (!is_array($input)) {
    throw new InvalidArgumentException('Invalid input must be string or array.');
  }

  $output = array();

  foreach ($input as $line => $string) {
    if (preg_match($pattern, $string)) {
      if ($context > 0) {
        $start = ($line - $context < 0) ? 0 : $line - $context;
        $end   = ($line + $context > count($input)) ? count($input) - 1 : $line + $context;

        $o = '';
        for ($start; $start <= $end; $start++) {
          $o .= $start + 1 . ': ' . $input[$start] . "\n";
        }
        $output[] = "\n" . $o;
      }
      else {
        $output[] = $line + 1 . ': ' . $string;
      }
    }
  }
  
  $output =  (empty($output)) ? FALSE : join($output, "\n\n----------------------\n\n");

  return $output;
}