Question 41282 in PHP Question posted in
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Recursively replace placeholder substrings based on related row data – PHP

I have this array:

$data = [
    ["id" => 1, "data" => "data 1"],
    ["id" => 2, "data" => "data <4>"],
    ["id" => 3, "data" => "data 3"],
    ["id" => 4, "data" => "<3>"]
];

I want to produce a new array. The resulting array should be:

[
    ["id" => 1, "data" => "data 1"],
    ["id" => 2, "data" => "data data 3"],
    ["id" => 3, "data" => "data 3"],
    ["id" => 4, "data" => "data 3"]
]

The idea is that each time there is <number> in the data attribute then this value should be replaced by the data attribute in the element which has the same id. In the example above, the last element is: ["id" => 4, "data" => "<3>"]

So we replace <3> with data 3 since it is what is stored in the data attribute of element with id => 3.

I have already created a function that works with the above array:

public function refProcess($data, &$newData, $i, &$tmpData){
    $dataLength = count($data);
    if($i>=$dataLength){
        return;
    }
    for(;$i<$dataLength;$i++){
        if(is_null($tmpData)){
            $tmpData = ['id'=> $data[$i]['id'], 'data'=>null];
        }

        if(strpos($data[$i]['data'],"[")!==false){

            $parsed = $this->getInbetweenStrings("<", ">", $data[$i]['data']);
            if(count($parsed)){

                foreach($parsed as $occurance){
                    foreach($data as $key => $dataValue){
                        if($dataValue['id']==$occurance){

                            if(strpos($dataValue['data'], "<")!==false){

                                $this->refProcess($data, $newData, $key, $tmpData);
                                $tmpData=null;
                            }
                            else{
                                
                                $tmpDataAtt = str_replace("<".$occurance.">", $dataValue['data'], $data[$i]['data']);
                                $tmpData['data'] = $tmpDataAtt;
                                $newData [] = $tmpData;
                                $tmpData = null;
                                break;
                            }
                        }
                    }
                    
                }
            }
        }
        else{
            $tmpData['data'] = $data[$i]['data'];
            $newData [] = $tmpData;
            $tmpData = null;
        }
    }//foreach
}

//returns an array contains strings existing between $start and $end. Multiple occurance
public function getInbetweenStrings($start, $end, $str){
$matches = array();
$regex = "/$start([a-zA-Z0-9_]*)$end/";
preg_match_all($regex, $str, $matches);
return $matches[1];
}

It works fine until I add another element to the array:

$data = [
    ["id" => 1, "data" => "data 1"],
    ["id" => 2, "data" => "data <4>"],
    ["id" => 3, "data" => "data 3"],
    ["id" => 4, "data" => "<3>"]
    ["id" => 5, "data" => "<2>"]
];

Element with id:5 the function goes into an endless loop. What am I missing?

The code can be tested at https://onlinephp.io/c/0da5d

Tags:

4

Answers


  1. 0

    You dont really do any recursive stuff, is a quit flat array structure you have.

    UPDATE: This was wrong, keep it just for the related comments:

    <?php

$data = [
    ["id" => 1, "data" => "data 1",],
    ["id" => 2, "data" => "data <4>",],
    ["id" => 3, "data" => "data 3",],
    ["id" => 4, "data" => "<3>",],
    ["id" => 5, "data" => "<2>",]
];
foreach ($data as &$set) {
    $set['data'] = preg_replace_callback('#.*(d+).*#', function ($m) {
         return 'data ' . $m[1];
    },$set['data']);
}
print_r($data);

    UPDATE:
    Here is now a working solution.

    <?php

$data = [
    ["id" => 1, "data" => "data 1",],
    ["id" => 2, "data" => "data <4>",],
    ["id" => 3, "data" => "data 3",],
    ["id" => 4, "data" => "<3>",],
    ["id" => 5, "data" => "<2>",],
    ["id" => 6, "data" => "data <7>",],#loop to 7
    ["id" => 7, "data" => "<6>",],#loop to 6
    ["id" => 8, "data" => "<0>",],#dead link
    ["id" => 9, "data" => "<10>",],#multi level loop
    ["id" => 10, "data" => "data <11>",],#multi level loop
    ["id" => 11, "data" => "<9>",],#multi level loop
];
#just for testing: order can be ignored
shuffle($data);
#step 1 make keys easy to access
$prepared = [];
$tmp=[];
foreach ($data as $set) {
    $prepared[$set['id']] = $set['data'];
    $tmp[$set['id']] = $set;
}
$data=$tmp;
#setp 2 replace values
$final = [];
do {
    foreach ($data as $k => &$set) {
        $set['data'] = preg_replace_callback('#(.*)<(d+)>#', function ($m) use ($prepared,$k) {
            #check for dead links
            if(!isset($prepared[$m[2]])){
                return $m[1]." ?{$m[2]}?";
            }
            #check for loop refer
            if(strpos($prepared[$m[2]],"<".$k.">")!==false){
                return $m[1]." §{$m[2]}§";
            }
            return $m[1].$prepared[$m[2]];
        }, $set['data']);
    
        if (strpos($set['data'], '>') === false) {
            $final[$k] = $set;
            unset($data[$k]);
        }
        
    }
 
} while (count($data));
ksort($final);
print_r($final);

    UPDATED:

    1. Now checks for dead links or loops and marks them.
    2. Added more prepare code, so order is now ignorable
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  2. 0

    Your code is way too complicated, there’s an easier approach. Note, I reindex the initial data to the key:id -> value:array, to avoid all those loops for finding the entry for required id.

    <?php
$data = [
    [
        "id"=>1,
        "data"=>"data 1",
    ],
    [
        "id"=>2,
        "data"=>"data <4>",
    ],
    [
        "id"=>3,
        "data"=>"data 3",
    ],
    [
        "id"=>4,
        "data"=>"<3>",
    ],
    [
        "id"=>5,
        "data"=>"<2>",
    ]
];

function getValue( $arr, $id ){

    // Required data contains placeholder, going deeper
    if( preg_match("/<d+>/", $arr[$id]['data']) ){
        return preg_replace_callback("/<(?<source_id>d+)>/", function( $matches ) use ($arr) {

            return getValue( $arr, $matches['source_id'] );

        }, $arr[$id]['data'] );
    }

    // Return raw value as-is
    return $arr[$id]['data'];
}


// Reindexing to get convinient access
$indexed_data = [];
foreach( $data as $entry )
    $indexed_data[ $entry['id'] ] = $entry;

// Resolving through recursive getValue function
foreach( $indexed_data as $id => &$entry )
    $entry['data'] = getValue( $indexed_data, $id );

// Output in desired format
print_r( array_values( $indexed_data ) );

    If there may be two entries with the same id, this approach not gonna work.

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  3. 0

    Your code is too clumsy to begin with. I would rather suggest a much simpler approach.

    • Index your array with id value as it’s key with array_column. This way, we can access any index with id of a particular value in O(1) time. This also gives you an advantage for the value of the id to be anything and not necessarily being symmetric with your subarray index key.

    • Capture the ID using regex. If there is a match, recurse again, else, our search ends here. Return it’s data value to the parent call and you are done.

    Snippet:

    <?php

$data = array_column($data, null, 'id');

foreach($data as $id => $d){
  getLeafNodeValue($id, $data);  
}

function getLeafNodeValue($id, &$data){
  $matches = [];
  if(preg_match('/<(d+)>/', $data[$id]['data'], $matches) === 1){
    $data[$id]['data'] = preg_replace('/<(d+)>/', getLeafNodeValue($matches[1], $data), $data[$id]['data']);
  }
  return $data[$id]['data'];
}

print_r($data);

    Online Demo

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  4. 0

    Here is a tidy recursive snippet that will modify your array by reference.

    Loop over the array (I am choosing to use array de-structuring syntax to declare individual row variables.

    If the needle is null or matches the row id, attempt the recursive replacement.

    If the needle matches a row’s id, return the value to the parent level, so that eventually the top level array is affected.

    Code: (Demo)

    function recurse(&$array, $needle = null) {
    foreach ($array as ['id' => $id, 'data' => &$data]) {
        if (($needle ?? $id) === $id) {
            $data = preg_replace_callback(
                '/<(d+)>/',
                fn($m) => recurse($array, (int) $m[1]),
                $data
            );
        }
        if ($needle === $id) {
            return $data;
        }
    }
}
recurse($array);
var_export($array);
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