According to its banner the version of PHP installed on the remote host is 5.3.x earlier than 5.3.4. Such versions are potentially affected by multiple vulnerabilities :
Binary data 5732.prm
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-7243
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2094
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2950
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3436
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3709
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3710
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3870
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4150
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4156
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4409
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4697
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4698
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4699
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-4700
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0753
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0754
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0755
www.php.net/ChangeLog-5.php#5.3.4
www.php.net/releases/5_3_4.php