PHP: searching in the first "column" of an array of arrays [duplicate] - php

Question

This question already has answers here:
PHP multidimensional array search by value
(23 answers)
Closed last year.
I have an array of arrays and I want to copy the first column
The data looks like this:
(0 => "homer", 1 => 1, 2 => 2, 3 => 3)
(0 => "marge", 1 => 2, 2 => 4, 3 => 8)
(0 => "bart", 1 => 6, 2 => 2, 3 => 7)
(0 => "lisa", 1 => 16, 2 => 20, 3 => 71)
Is there a PHP function (similar to array_search) which I can use to search for a name match in the first "column" ?
The data in the first column is already sorted so if I could copy "column1", I could carry out a array_search (which I assume uses a bsearch, rather than a naive element by element iteration).
My questions are:
Is there a PHP function similar to array_search, which I can use to search for matching items in the 1st column of the 2D array?
Failing that, is there a PHP function to copy the first column into a 1D array (whilst preserving order) so I can call array_search on it ?

Answer 1

Is there a PHP function similar to array_search, which I can use to search for matching items in the 1st column of the 2D array?
You could use array_filter
$matchedArray = array_filter($myArray, function($x) use ($nameToSearchFor) {
return $x[0] == $nameToSearchFor;
});
Then given:
$myArray = array(
array(0=>"homer", 1=> 1, 2=> 2, 3=> 3),
array(0 => "marge", 1=> 2, 2 => 4, 3=> 8),
array(0 => "bart", 1 => 6, 2 => 2, 3 => 7),
array(0 => "lisa", 1 => 16, 2 => 20, 3 => 71),
);
$nameToSearchFor = "bart";
Would produce:
$matchedArray === array(0 => "bart", 1 => 6, 2 => 2, 3 => 7);
I've used closures, that only work in PHP 5.3.0, but you use a traditional callback or create_function in older versions of php
Failing that, is there a PHP function to copy the first column into a 1D array (whilst preserving order) so I can call array_search on it ?
See deceze's first option. I see no need repeating a perfectly good answer.

Answer 2

$oneDarray = array_map(create_function('$a', 'return $a[0];'), $twoDarray);
Or:
foreach ($twoDarray as $values) {
if ($values[0] == 'homer') {
// found!
break;
}
}

Answer 3

This question came top on my Google search for array search column. It took me some time to find this better answer to the same question. By Mark M.
If you are using PHP >= 5.5, then you can use the new array_column(), >in conjunction with array_keys() and array_map().
Applied to this question, to search for "bart", it would be:
$array=array(
array(0=>"homer", 1=> 1, 2=> 2, 3=> 3),
array(0 => "marge", 1=> 2, 2 => 4, 3=> 8),
array(0 => "bart", 1 => 6, 2 => 2, 3 => 7),
array(0 => "lisa", 1 => 16, 2 => 20, 3 => 71));
$result = $array[array_search("bart",array_column($array, 0))];
print_r($result);
/* Output:
Array
(
[0] => bart
[1] => 6
[2] => 2
[3] => 7
)
*/
Run demo

Answer 4

PHP doesn't have a good clean way of doing this that I know of. However, you can do it yourself using a binary-search since the array is already sorted by the values in the first column of its child arrays. Here is the code to accomplish this:
<?php
// Binary Search Taken By greenmr:
// http://php.net/manual/en/function.array-search.php#89413
function array_bsearch( $needle, $haystack, $comparator ) {
$high = Count( $haystack ) -1;
$low = 0;
while ( $high >= $low ){
$probe = Floor( ( $high + $low ) / 2 );
$comparison = $comparator( $haystack[$probe], $needle );
if ( $comparison < 0 ) {
$low = $probe +1;
} elseif ( $comparison > 0 ) {
$high = $probe -1;
} else {
return $probe;
}
}
return -1;
}
// Compare the needle the first element/column
function KeyCompare( $obj, $needle) {
if ( $obj[0] < $needle ) {
return -1;
} elseif ( $obj[0] > $needle ) {
return 1;
} else {
return 0;
}
}
$arr = array(array(0=>"homer", 1=> 1, 2=> 2, 3=> 3),
array(0 => "marge", 1=> 2, 2 => 4, 3=> 8),
array(0 => "bart", 1 => 6, 2 => 2, 3 => 7),
array(0 => "lisa", 1 => 16, 2 => 20, 3 => 71));
$index = array_bsearch( 'marge', $arr, 'KeyCompare' );
// prints the array containing marge
echo print_r($arr[$index]);
?>

Answer 5

You could convert the array to use keys using an array_walk
$new_data = array();
array_walk($data, create_function('a','$new_data[$a[0]] = $a;'));
$search_text = 'bart';
if (array_key_exists($new_data, $search_text)) {
echo "I found '$search_text': ".print_r($new_data[$search_text], true);
}