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)));}?>
(PHP 4, PHP 5, PHP 7, PHP 8)
preg_grep — Devuelve un array con los resultados de la búsqueda
preg_grep() devuelve un array que contiene
los elementos de array
que satisfacen el patrón pattern.
patternEl patrón a buscar, en forma de string.
arrayEl array de entrada.
flags
Si esta opción tiene el valor PREG_GREP_INVERT,
esta función devuelve los elementos del array
input que no coinciden
con el patrón
pattern.
Devuelve un array indexado, utilizando las claves del
array array de entrada, o false si ocurre un error.
Si el patrón regex pasado no se compila a una regex válida, se emite una E_WARNING.
Ejemplo #1 Ejemplo con preg_grep()
<?php
$array = [ "4", M_PI, "2.74", 42 ];
// devuelve todos los elementos del array que contienen números de punto flotante
$fl_array = preg_grep("/^(\d+)?\.\d+$/", $array);
var_dump($fl_array);
?>
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