$re = '/<\s*span[^>]*>(.*?)<\s*\/\s*span\s*>/m';
$str = '<p nameIt="Title">Title_Test</p><figure class="t15"><table><thead><tr>
<th><span>Column1</span></th><th><span>Column2</span></th></tr></thead><tbody><tr><td><span>Entry1</span></td><td><span>Entry2</span></td><td><span>ready</span></td></tr><tr><td><span style="some:style;">Entry3</span></td><td><span style="another:style;">Entry4</span></td></tr></tbody></table></figure><p ex="ready">!aaa; ';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php