Try the PHP Toolkit for i5/OS. There is a older Redbook that describes it: http://www.redbooks.ibm.com/redbooks/pdfs/sg247327.pdf
An example from there:
<HTML>
<?php
/* Connect to server */
$conn = i5_connect("localhost", "PHPUSER", "MYPASSWORD");
if (!$conn)
die("<br>Connection using \"localhost\" with USERID and PASSWORD failed. Error
number =".i5_errno()." msg=".i5_errormsg())."<br>";
else
echo "<br>Connection using \"localhost\" with USERID and PASSWORD OK!<br>\n";
/* Call Retrieve Network Attributes command */
$ret = i5_command("rtvneta", array(), array("sysname" => "sysn", "lclnetid"=>"lclnet"));
if (!$ret) die("<br>rtvneta command failed. errno=".i5_errno()."
msg=".i5_errormsg());
print "<h1><b>Results of \"rtvneta\" command </b></h1><br>" ;
print "System Name : $sysn<br>" ;
print "Local Net ID : $lclnet<br>" ;
/* Close connection */
i5_close($conn);
?>
</HTML>