With only 4 PHP job offers at present in Bilbao, it might be worthwhile to check out job offers in similar domains. Why not check out the most dominant categories of Data analysis and Programmer, that the range of jobs can be broken down to. Job offers that require Drupal, MySQL, or WordPress are often mentioned in job offers in this area.
This is not the best time to search for PHP internship opportunities. Employers are now almost exclusively recruiting accomplished job seekers. Although startups are a rising trend, there aren't any currently advertising for PHP. Use the region map at the top of the page to see where the offices are located.