title: How to prin RRD Graph data with PHP
body: <p>Thanks in advance for your time and effort. This is my first script with PHP and RRD's. While I was writing a short program for SNMP I came across with RRD a powerful tool for graphical output. I tried to wright a short operating script to imitate the output of a graph. I read as much as possible documentations regarding RRD from the official page and tried to add them to my PHP code. I have found some functions while I was trying to debug my code which are showing that my data are coming in normally and cased on reference as expected. Sample provided under:</p>
  
  <pre><code>["last_update"]=&gt;
  int(1396917542)
  ["ds_cnt"]=&gt;
  int(3)
  ["ds_navm"]=&gt;
  array(3) {
    [0]=&gt;
    string(10) "ifInOctets"
    [1]=&gt;
    string(11) "ifOutOctets"
    [2]=&gt;
    string(9) "sysUpTime"
  }
  ["data"]=&gt;
  array(3) {
    [0]=&gt;
    string(4) "1405"
    [1]=&gt;
    string(4) "1219"
    [2]=&gt;
    string(4) "1893"
   }
  }
  </code></pre>
  
  <p>Based on function:</p>
  
  <pre><code>"$debug = rrd_lastupdate (
                            "".$rrdFile.""
               );"
  </code></pre>
  
  <p>I am having difficulties to understand since the input is coming correctly and there is not print error displayed while compiling my code why I do not get any output?</p>
  
  <p>I have included my working code as example for possible reproduction and better understanding of my error.</p>
  
  <pre><code>&lt;?php
  
  // rrdtool info /var/www/snmp.rrd Debugging command
  
  while (1) {
    sleep (1);
    $file = "snmp";
    $rrdFile = dirname(__FILE__) . "/".$file.".rrd";
    $in = "ifInOctets";
    $out = "ifOutOctets";
    $count = "sysUpTime";
  
    $options = array(
         "--start","now -10s", // Now -10 seconds (default)
         "--step", "10", // Step size of 300 seconds 5 minutes
         "DS:".$in.":COUNTER:20:U:U",
         "DS:".$out.":COUNTER:20:U:U",
         "DS:".$count.":COUNTER:20:U:U",
         /* DS:ds-name:DST:dst arguments
            (DST: GAUGE, COUNTER, DERIVE, and ABSOLUTE):heartbeat:min:max
            heartbeat: in case that there is not input up to 600 seconds
            then the input will characterised as undefined (blank)
            Based on Nyquist rate (Fs &gt;= 2 * Fmax) 300 (step) 600 (heartbeat)
            32-bit = 2^32-1 = 4294967295 (counter ticks)
            64-bit = 2^64-1 = 18446744073709551615 (counter ticks)
            64-bit counter (caution!!!) different oid's
         */
         "RRA:MIN:0.5:10:300",
         "RRA:MIN:0.5:20:600",
         "RRA:MAX:0.5:10:300",
         "RRA:MAX:0.5:20:600",
         "RRA:AVERAGE:0.5:10:300",
         "RRA:AVERAGE:0.5:20:600",
         /* RRA:AVERAGE | MIN | MAX | LAST:xff:steps:rows
            xff range: 0-1 (exclusive) defines the allowed number of unknown
            *UNKNOWN* PDPs to the number of PDPs in the interval. Step defines
            how many of those data points are used to build consolidated data.
            rows defines how many data values are kept in an RRA.
         */
         );
  
    //create rrd file
    $create = rrd_create(
             "".$rrdFile."",
             $options
             );
  
    if ($create === FALSE) {
      echo "Creation error: ".rrd_error()."\n";
    }
  
    $ifInOctets = rand(0, 1500); // ifInOctets (OID: 1.3.6.1.2.1.2.2.1.10)
    $ifOutOctets = rand(0, 2500); // ifOutOctets (OID: 1.3.6.1.2.1.2.2.1.16)
    $sysUpTime = rand(0, 2000); // sysUpTime (OID: 1.3.6.1.2.1.1.3)
  
    $t = time();
  
    //update rrd file
    $update = rrd_update(
             "".$rrdFile."",
             array(
               /* Update database with 3 values 
              based on time now (N:timestamp) */
               "".$t.":".$ifInOctets.":".$ifOutOctets.":".$sysUpTime.""
               )
             );
  
    if ($update === FALSE) {
      echo "Update error: ".rrd_error()."\n";
    }
  
    $start = "now";
    $title = "Hourly Server Data";
  
    $final = array(
       "--start","".$start." -10s",
       "--step","10",
       "--title=".$title."",
       "--vertical-label=Bytes/sec",
       "--lower-limit=0",
       //"--no-gridfit",
       "--slope-mode",
       //"--imgformat","EPS",
       "DEF:".$in."_def=".$file.".rrd:".$in.":AVERAGE",
       "DEF:".$out."_def=".$file.".rrd:".$out.":AVERAGE",
       "DEF:".$count."_def=".$file.".rrd:".$count.":AVERAGE",
       "CDEF:inbits=".$in."_def,8,*",
       "CDEF:outbits=".$out."_def,8,*",
       "CDEF:counter=".$count."_def,8,*",
       /* "VDEF:".$in_min."=inbits,MINIMUM",
          "VDEF:".$out_min."=outbits,MINIMUM",
          "VDEF:".$in_max."=inbits,MAXIMUM",
          "VDEF:".$out_max."=outbits,MAXIMUM",
          "VDEF:".$in_av."=inbits,AVERAGE",
          "VDEF:".$out_av."=outbits,AVERAGE", */
       "COMMENT:\\n",
       "LINE:".$in."_def#FF00FF:".$in."",
       "GPRINT:inbits:LAST:last \: %6.2lf %SBps",
       "COMMENT:\\n",
       "LINE:".$out."_def#0000FF:".$out."",
       "GPRINT:outbits:LAST:last \: %6.2lf %SBps",
       "COMMENT:\\n",
       "LINE:".$count."_def#FFFF00:".$count."",
       "GPRINT:counter:LAST:last\: %6.2lf %SBps",
       "COMMENT:\\n",
       );
  
    // graph output 
    $outputPngFile = rrd_graph(
               "".$file.".png",
               $final
               );
  
    if ($outputPngFile === FALSE) {
      echo "&lt;b&gt;Graph error: &lt;/b&gt;".rrd_error()."\n";
     }
  
    /*  Returns the first data sample from the 
        specified RRA of the RRD file. */
     $result = rrd_first (
             $rrdFile,
             $raaindex = 0
             );
  
     if ($result === FALSE) {
       echo "&lt;b&gt;Graph result error: &lt;/b&gt;".rrd_error()."\n";
     }
  
     /* Returns the UNIX timestamp of the most 
        recent update of the RRD database. */
     $last = rrd_last (
          $rrdFile
          );
  
     if ($last === FALSE) {
        echo "&lt;b&gt;Graph result error: &lt;/b&gt;".rrd_error()."\n";
      }
  
      $info = rrd_info (
          "".$rrdFile.""
          );
  
      if ($info === FALSE) {
        echo "&lt;b&gt;Graph result error: &lt;/b&gt;".rrd_error()."\n";
      }
  
      /*  Gets array of the UNIX timestamp and the values stored 
          for each date in the most recent update of the RRD database file. */
      $debug = rrd_lastupdate (
             "".$rrdFile.""
             );
  
       if ($debug === FALSE) {
         echo "&lt;b&gt;Graph result error: &lt;/b&gt;".rrd_error()."\n";
       }
  
       var_dump ($debug);
  
       /* $version = rrd_version ( );
          echo "This is the version ".$version."\n"; */
  
  } // End of while condition 
  ?&gt;
  </code></pre>