preg_grep

A shorter way to run a match on the array's keys rather than the values:<?phpfunction preg_grep_keys($pattern, $input, $flags = 0) {    return array_intersect_key($input, array_flip(preg_grep($pattern, array_keys($input), $flags)));}?>

Run a match on the array's keys rather than the values:<?phpfunction preg_grep_keys( $pattern, $input, $flags = 0 ){    $keys = preg_grep( $pattern, array_keys( $input ), $flags );    $vals = array();    foreach ( $keys as $key )    {        $vals[$key] = $input[$key];    }    return $vals;}?>

This may be obvious to most experienced developers,but just in case its not,when using preg_grep to check for whitelisted items ,one must be very careful to explicitly define the regex boundaries or it will fail<?php$whitelist = ["home","dashboard","profile","group"];$possibleUserInputs = ["homd","hom","ashboard","settings","group"];foreach($possibleUserInputs as  $input){     if(preg_grep("/$input/i",$whitelist)    {         echo $input." whitelisted";    }else{         echo $input." flawed";    }}?>This results in:homd flawedhom whitelistedashboard whitelistedsettings flawedgroup whitelistedI think this is because if boundaries are not explicitly defined,preg_grep looks for any instance of  the substring in the whole array and returns true if found.This is not what we want,so boundaries must be defined.<?phpforeach($possibleUserInputs as  $input){     if(preg_grep("/^$input$/i",$whitelist)    {         echo $input." whitelisted";    }else{         echo $input." flawed";    }}?>this results in:homd flawedhom flawedashboard flawedsettings flawedgroup whitelistedin_array() will also give the latter results but will require few tweaks if say,the search is to be case insensitive,which is always the case 70% of the time