According to its banner, the version of PHP 5.x installed on the remote host is older than 5.2.6. Such versions may be affected by the following issues :
Binary data 4493.prm
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4850
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0599
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0674
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-2050
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-2051
www.openwall.com/lists/oss-security/2008/05/02/2
www.php.net/releases/5_2_6.php