Kurz und einfach:

<?php

if($sql = mysql_connect($sql_host, $sql_user,$sql_pswd)){
mysql_select_db($sql_name);
$s = mysql_query("EXPLAIN SELECT * FROM tabelle LIMIT 1");
$fetch = mysql_fetch_object($s);
$eintraege = $fetch->rows;
print $eintraege;
mysql_close($sql);
}

?>