Tutorial :php array_merge without erasing values?


Background: Trevor is working with a PHP implementation of a standard algorithm: take a main set of default name-value pairs, and update those name-value pairs, but only for those name-value pairs where a valid update value actually exists.

Problem: by default, PHP array_merge works like this ... it will overwrite a non-blank value with a blank value.

$aamain   =   Array('firstname'=>'peter','age'=>'32','nation'=>'');  $update   =   Array('firstname' => '','lastname' => 'griffin', age =>'33','nation'=>'usa');    print_r(array_merge($aamain,$update));      /*  Array  (      [firstname] =>           // <-- update set this to blank, NOT COOL!      [age] => 33              // <-- update set this to 33, thats cool      [lastname] => griffin    // <-- update added this key-value pair, thats cool      [nation] => usa          // <-- update filled in a blank, thats cool.  )  */  

Question: What's the fewest-lines-of-code way to do array_merge where blank values never overwrite already-existing values?

print_r(array_coolmerge($aamain,$update));      /*  Array  (      [firstname] => peter  // <-- don't blank out a value if one already exists!      [age] => 33      [lastname] => griffin      [nation] => usa    )  */  

UPDATE: 2016-06-17T11:51:54 the question was updated with clarifying context and rename of variables.


Well, if you want a "clever" way to do it, here it is, but it may not be as readable as simply doing a loop.

$merged = array_merge(array_filter($foo, 'strval'), array_filter($bar, 'strval'));  

edit: or using +...


Try this:

$merged = array_map(      create_function('$foo,$bar','return ($bar?$bar:$foo);'),      $foobar,$feebar  );  

Not the most readable solution, but it should replace only non-empty values, regardless of which order the arrays are passed..


Adjust to your needs:

# Replace keys in $foo  foreach ($foo as $key => $value) {      if ($value != '' || !isset($bar[$key])) continue;      $foo[$key] = $bar[$key];  }    # Add other keys in $bar  # Will not overwrite existing keys in $foo  $foo += $bar;  


array_replace_recursive($array, $array2);  

This is the solution.


This will put duplicates into a new array, I don't know if this is what you want though.

<?php    $foobar =   Array('firstname' => 'peter','age' => '33',);    $feebar =   Array('firstname' => '','lastname' => 'griffin',);    $merged=$foobar;    foreach($feebar as $k=>$v){      if(isset($foobar[$k]))$merged[$k]=array($v,$foobar[$k]);      else $merged[$k]=$v;    }    print_r($merged);  ?>  

This will simply assure that feebar will never blank out a value in foobar:

<?php    $foobar =   Array('firstname' => 'peter','age' => '33',);    $feebar =   Array('firstname' => '','lastname' => 'griffin',);    $merged=$foobar;    foreach($feebar as $k=>$v) if($v)$merged[$k]=$v;    print_r($merged);  ?>  

or ofcourse,

<?    function cool_merge($array1,$array2){      $result=$array1;      foreach($array2 as $k=>$v) if($v)$result[$k]=$v;      return $result;    }      $foobar =   Array('firstname' => 'peter','age' => '33',);    $feebar =   Array('firstname' => '','lastname' => 'griffin',);    print_r(cool_merge($foobar,$feebar));  ?>  


If you also want to keep the values that are blank in both arrays:

array_filter($foo) + array_filter($bar) + $foo + $bar  

Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
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