Pattern Match on a Array Key

Question

I need to get the stock values out of this array:

Array ( 
[stock0] => 1
[stockdate0] => 
[stock1] => 3 
[stockdate1] => apple 
[stock2] => 2 [
stockdate2] => 
) 

I need to pattern match on this array, where the array key = "stock" + 1 wildcard character. I have tried using the array filter function to get every other value on the PHP manual but the empty values seem to throw it out. I tried alot of different things I found but nothing is working.

Can this be done?

Answer 1

<?php

$foo = 
array ( 
'stock0' => 1,
'stockdate0' => 1,
'stock1' => 3,
'stockdate1' => 2,
);

$keys = array_keys( $foo );
foreach ( $keys as $key ) {
    if ( preg_match( '/stock.$/', $key ) ) {
    var_dump( $key );
    }
}

I'm hoping I interpreted correctly and you wanted 'stock', 1 wildcard character thats not a newline, then end of string.

Answer 2

You should store those as:

Array(
  [0] => Array(
    stock => 1,
    stockdate => ...
  ),
  [1] => Array(
    stock => 3,
    stockdate => apple
  ),
  ...
)

Answer 3

Since PHP 5.6.0 the flag option has been added to array_filter. This allows you to filter based on the array keys rather than its values:

array_filter($items, function ($key) {
  return preg_match('/^stock\d$/', $key);
}, ARRAY_FILTER_USE_KEY);

Answer 4

array_filter does not have access to the key and therefore is not the right tool for your job.

I belive what you're looking to do is this:

$stocks = Array ( 
"stock0" => 1,
"stockdate0" => '',
"stock1" => 3, 
"stockdate1" => 'apple',
"stock2" => 2,
"stockdate2" => ''
);


$stockList = array();  //Your list of "stocks" indexed by the number found at the end of "stock"

foreach ($stocks as $stockKey => $stock)
{
  sscanf($stockKey,"stock%d", &stockId);  // scan into a formatted string and return values passed by reference
  if ($stockId !== false)
     $stockList[$stockId] = $stock;
}

Now $stockList looks like this:

Array ( 
[0] => 1
[1] => 3 
[2] => 2 
)

You may need to fuss with it a bit, but I think this is what you are asking for.

HOWEVER, you really should be following Jeff Ober's advice if you have the option to do so.

Answer 5

# returns array('stock1' => 'foo')
array_flip(preg_grep('#^stock.$#', array_flip(array('stock1' => 'foo', 'stockdate' => 'bar'))))

Not sure how good the performance is due to the regex and two flips, but excellent maintainability (no bug hunting in loops).

Answer 6

Ok working solution: Green for ChronoFish!

 $stockList = array();  //Your list of "stocks" indexed by the number found at the end of "stock"

foreach ($stock as $stockKey => $stock)
{
  sscanf($stockKey,"message%d", $stockId);  // scan into a formatted string and return values passed by reference
  if ($stockId !== false) {
     $stockList[$stockId] = $stock;
}

$stockList=array_values($stockList); //straightens array keys out
$stockList = array_slice ($stockList, "0", $count); //gets rid of blank value generated at end of array (where $count = the array's orginal length)
print_r ($stockList);

Answer 7

To allow numeric suffixes that exceed 9, you can use rtrim() instead of regex to remove the numeric suffix, then check for an identical match again the search string.

Code: (Demo)

$stocks = [
    "stock0" => 1,
    "stockdate0" => '',
    "stock1" => 3, 
    "stockdate1" => 'apple',
    "stock4DON'TMATCHTHIS!!!" => 4,
    "stock2" => 2,
    "stockdate2" => '',
    "stock33" => 333,
    "stockdate33" => ''
];

$find = 'stock';
var_export(
    array_filter($stocks, fn($k) => rtrim($k, '0..9') === $find, ARRAY_FILTER_USE_KEY)
);

Output:

array (
  'stock0' => 1,
  'stock1' => 3,
  'stock2' => 2,
  'stock33' => 333,
)