selecting an array key based on partial string

you would have to iterate over your array to check each key separately, since you don't have the possibility to query the array directly (I'm assuming the array also holds totally unrelated keys, but you can skip the if part if that's not the case):

foreach($array as $k => $v)
{
  if (strpos($k, 'show_me_') !== false)
  {
    $number = substr($k, strrpos($k, '_'));
  }
}

However, this sounds like a very strange way of storing data, and if I were you, I'd check if there's not an other way (more efficient) of passing data around in your application ;)

I ran into a similar problem recently. This is what I came up with:

$value = $my_array[current(preg_grep('/^show_me_/', array_keys($my_array)))];

one solution i can think of:

foreach($myarray as $key=>$value){
  if("show_me_" == substr($key,0,8)){
    $number = substr($key,strrpos($key,'_'));
    // do whatever you need to with $number...
  }
}

to search for certain string in array keys you can use array_filter(); see docs

// the array you'll search in
$array = ["search_1"=>"value1","search_2"=>"value2","not_search"=>"value3"];
// filter the array and assign the returned array to variable
$foo = array_filter(
    // the array you wanna search in
    $array, 
    // callback function to search for certain sting
    function ($key){ 
        return(strpos($key,'search_') !== false);
    }, 
    // flag to let the array_filter(); know that you deal with array keys
    ARRAY_FILTER_USE_KEY
);
// print out the returned array
print_r($foo);

if you search in the array values you can use the flag 0 or leave the flag empty

$foo = array_filter(
    // the array you wanna search in
    $array, 
    // callback function to search for certain sting
    function ($value){ 
        return(strpos($value,'value') !== false);
    }, 
    // flag to let the array_filter(); know that you deal with array value
    0
);

or

$foo = array_filter(
    // the array you wanna search in
    $array, 
    // callback function to search for certain sting
    function ($value){ 
        return(strpos($value,'value') !== false);
    }
);

if you search in the array values and array keys you can use the flag ARRAY_FILTER_USE_BOTH

$foo = array_filter(
    // the array you wanna search in
    $array, 
    // callback function to search for certain sting
    function ($value, $key){ 
        return(strpos($key,'search_') !== false or strpos($value,'value') !== false);
    },
    ARRAY_FILTER_USE_BOTH
);

in case you'll search for both you have to pass 2 arguments to the callback function