PHP Warning: array_combine() and array_merge() generating warning

Question

The below code is generating several of the below error and it's pointing to

PHP Warning: array_merge(): Expected parameter 1 to be an array, null given in /home/mike/snmpCode.php on line 20

PHP Warning: array_combine(): Both parameters should have an equal number of elements in /home/mike/snmpCode.php on line 20

#!/usr/bin/php
<?PHP

$data = snmp3_real_walk (
    'localhost',
    'User3',
    'authPriv',
    'MD5',
    'pwd123',
    'DES',
    'pwd123',
    'ETRA-VRTR-MIB::vRtrIfName'
);

print_r($data);

$Array = array();

foreach($data as $key => $val) {
    $newval = explode(':',trim($val, 'STRING: '));
    $newkey = explode(' ',trim($key, '[ETRA-VRTR-MIB::vRtrIfName.]'));
    $Array = array_merge($Array, array_combine($newkey, $newval));
}

$data = $Array;

print_r($data);

?>

The seems to point to $Array = array_merge($Array, array_combine($newkey, $newval));

I can't seem to figure out the issue.

Below is the array from the snmp3_real_walk(), printout of $data after assigning the return from snmp3_real_walk() function.

Array
(
    [ETRA-VRTR-MIB::vRtrIfName.1.1] => STRING: "intf1"
    [ETRA-VRTR-MIB::vRtrIfName.1.2] => STRING: "intf2"
    [ETRA-VRTR-MIB::vRtrIfName.1.3] => STRING: "intf3"
    [ETRA-VRTR-MIB::vRtrIfName.1.4] => STRING: "intf4"
    [ETRA-VRTR-MIB::vRtrIfName.1.6] => STRING: "intf5"
    [ETRA-VRTR-MIB::vRtrIfName.1.7] => STRING: "intf6"
    [ETRA-VRTR-MIB::vRtrIfName.1.8] => STRING: "intf7"
    [ETRA-VRTR-MIB::vRtrIfName.1.9] => STRING: "intf8"
    [ETRA-VRTR-MIB::vRtrIfName.1.10] => STRING: "intf9"
    [ETRA-VRTR-MIB::vRtrIfName.1.11] => STRING: "intf10"
    [ETRA-VRTR-MIB::vRtrIfName.1.12] => STRING: "intf11"
    [ETRA-VRTR-MIB::vRtrIfName.1.13] => STRING: "intf12"
    [ETRA-VRTR-MIB::vRtrIfName.1.14] => STRING: "intf13"
    [ETRA-VRTR-MIB::vRtrIfName.1.15] => STRING: "intf14"
    [ETRA-VRTR-MIB::vRtrIfName.1.19] => STRING: "intf15"
    [ETRA-VRTR-MIB::vRtrIfName.1.39] => STRING: "intf16"
    [ETRA-VRTR-MIB::vRtrIfName.1.64] => STRING: "intf17"
)

Instead of assigning $data to the snmp_walk function return and create an array like the below, I don't have any issue.

$data = array(
    '[ETRA-VRTR-MIB::vRtrIfName.1.1]' => 'STRING: "intf1"', 
    '[ETRA-VRTR-MIB::vRtrIfName.1.2]' => 'STRING: "intf2"'
);

Can you please help?

You should compare the return value of snmp3_real_walk() to the array you expect it to return. Use var_dump() on both, and see where they differ. If I mock the array from the print_r() output, then your code runs without warnings or errors. I have not checked it for any potential logic issues. — Ro Achterberg
– Ro Achterberg, Commented Nov 5, 2020 at 7:34
From the array_combine() documentation: "Returns the combined array, FALSE if the number of elements for each array isn't equal." Since the two arrays are of different length, array_combine() returns NULL, and when you merge that with $Array you get NULL, which you are then storing back in $Array, which then causes problems on the next iteration. — kmoser
– kmoser, Commented Nov 5, 2020 at 7:36

KodeFor.Me · Accepted Answer · 2020-11-05 07:40:20Z

0

Unfortunately, your English description is not really good, and I am not 100% sure of what you want to do.

So far, what I understood is that the function snmp3_real_walk returns back to you an array with the following data:

Array
(
    [ETRA-VRTR-MIB::vRtrIfName.1.1] => STRING: "intf1"
    [ETRA-VRTR-MIB::vRtrIfName.1.2] => STRING: "intf2"
    [ETRA-VRTR-MIB::vRtrIfName.1.3] => STRING: "intf3"
    [ETRA-VRTR-MIB::vRtrIfName.1.4] => STRING: "intf4"
    [ETRA-VRTR-MIB::vRtrIfName.1.6] => STRING: "intf5"
    [ETRA-VRTR-MIB::vRtrIfName.1.7] => STRING: "intf6"
    [ETRA-VRTR-MIB::vRtrIfName.1.8] => STRING: "intf7"
    [ETRA-VRTR-MIB::vRtrIfName.1.9] => STRING: "intf8"
    [ETRA-VRTR-MIB::vRtrIfName.1.10] => STRING: "intf9"
    [ETRA-VRTR-MIB::vRtrIfName.1.11] => STRING: "intf10"
    [ETRA-VRTR-MIB::vRtrIfName.1.12] => STRING: "intf11"
    [ETRA-VRTR-MIB::vRtrIfName.1.13] => STRING: "intf12"
    [ETRA-VRTR-MIB::vRtrIfName.1.14] => STRING: "intf13"
    [ETRA-VRTR-MIB::vRtrIfName.1.15] => STRING: "intf14"
    [ETRA-VRTR-MIB::vRtrIfName.1.19] => STRING: "intf15"
    [ETRA-VRTR-MIB::vRtrIfName.1.39] => STRING: "intf16"
    [ETRA-VRTR-MIB::vRtrIfName.1.64] => STRING: "intf17"
)

But when you run the foreach look you get too many warnings of type:

PHP Warning: array_merge(): Expected parameter 1 to be an array, null given in /home/mike/snmpCode.php on line 20

PHP Warning: array_combine(): Both parameters should have an equal number of elements in /home/mike/snmpCode.php on line 20

Based on the data you shared, I have written the following code, that is running smoothly, and without warnings:

// I have comment out this code on my local, because I don't have 
// the implementation you use on your own development environment:
//
// $data = snmp3_real_walk (
//     'localhost',
//     'User3',
//     'authPriv',
//     'MD5',
//     'pwd123',
//     'DES',
//     'pwd123',
//     'ETRA-VRTR-MIB::vRtrIfName'
// );

// By this code, I have simulated the output of the data you have provide 
// in your example:
$data = [
    "ETRA-VRTR-MIB::vRtrIfName.1.1" => "STRING: intf1",
    "ETRA-VRTR-MIB::vRtrIfName.1.2" => "STRING: intf2",
    "ETRA-VRTR-MIB::vRtrIfName.1.3" => "STRING: intf3",
    "ETRA-VRTR-MIB::vRtrIfName.1.4" => "STRING: intf4",
    "ETRA-VRTR-MIB::vRtrIfName.1.6" => "STRING: intf5",
    "ETRA-VRTR-MIB::vRtrIfName.1.7" => "STRING: intf6",
    "ETRA-VRTR-MIB::vRtrIfName.1.8" => "STRING: intf7",
    "ETRA-VRTR-MIB::vRtrIfName.1.9" => "STRING: intf8",
    "ETRA-VRTR-MIB::vRtrIfName.1.10" => "STRING: intf9",
    "ETRA-VRTR-MIB::vRtrIfName.1.11" => "STRING: intf10",
    "ETRA-VRTR-MIB::vRtrIfName.1.12" => "STRING: intf11",
    "ETRA-VRTR-MIB::vRtrIfName.1.13" => "STRING: intf12",
    "ETRA-VRTR-MIB::vRtrIfName.1.14" => "STRING: intf13",
    "ETRA-VRTR-MIB::vRtrIfName.1.15" => "STRING: intf14",
    "ETRA-VRTR-MIB::vRtrIfName.1.19" => "STRING: intf15",
    "ETRA-VRTR-MIB::vRtrIfName.1.39" => "STRING: intf16",
    "ETRA-VRTR-MIB::vRtrIfName.1.64" => "STRING: intf17"
];
$Array = [];

foreach($data as $key => $val) {
    $newval = explode(':',trim($val, 'STRING: '));
    $newkey = explode(' ',trim($key, '[ETRA-VRTR-MIB::vRtrIfName.]'));

    // By the following if statement, I try to eliminate the warnings by 
    // checking if both values exist.
    if ( $newkey && $newval ) {
        $newArray = array_combine($newkey, $newval);

        // Finally to further eliminate the warnings, I try to make sure that the
        // $newArray has been created.
        if ( $newArray ) {
            $Array = array_merge($Array, $newArray);
        }
    }
}

$data = $Array;

print_r($data);

The output of the above code on my local environment is like that:

So, if still have errors, then maybe you have to check what is the actual output of the function snmp3_real_walk, because it may return some unexpected results.

Hope this code helps you.

answered Nov 5, 2020 at 7:40

KodeFor.Me

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5 Comments

Mike T Over a year ago

Thank you KodeFor.me, kmoser, and Ro Achterberg. I see the issue. I didn't post the complete array return for snmp3_real_walk function. I just dumped and noticed that one of the return has [ETRA-VRTR-MIB::vRtrIfName.2.24] => STRING: "to-vprn-2:1218". And my code has $newval = explode(' ',trim($val, 'STRING :')); which should retain only the interface name. However since there is another ":" char in the interface name, it doesn't retain the interface name. Trying to figure out how to retain only "to-vprn-2:1218". If anyone can help, I would appreciate.

KodeFor.Me Over a year ago

Did you consider using regular expressions to match what you need? Maybe this way is simpler to get the information you want.

Mike T Over a year ago

Thanks. Got it to work using regular expression. $re = '/STRING: ([^ ]+)/'; preg_match($re, $val, $newval); $newval = array($newval[1]);

KodeFor.Me Over a year ago

@MikeT if you got an answer and you want, don't forget to update or mark the answer as the right on using the checkmark below the voting controls :) Thank you in advance ! :)

Mike T Over a year ago

Thank you KodeFor.Me :) I'd thought I'd done that. Just did it.

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