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preg_grep

(PHP 4, PHP 5, PHP 7, PHP 8)

preg_grepReturn array entries that match the pattern

Descrição

preg_grep(string $pattern, array $array, int $flags = 0): array|false

Returns the array consisting of the elements of the array array that match the given pattern.

Parâmetros

pattern

The pattern to search for, as a string.

array

The input array.

flags

If set to PREG_GREP_INVERT, this function returns the elements of the input array that do not match the given pattern.

Valor Retornado

Returns an array indexed using the keys from the array array, ou false em caso de falha.

Erros/Exceções

Se o padrão de expressão regular passado não for compilado para uma expressão regular válida, um E_WARNING será emitido.

Exemplos

Exemplo #1 preg_grep() example

<?php
// return all array elements
// containing floating point numbers
$fl_array = preg_grep("/^(\d+)?\.\d+$/", $array);
?>

Veja Também

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User Contributed Notes 4 notes

up
73
Daniel Klein
10 years ago
A shorter way to run a match on the array's keys rather than the values:

<?php
function preg_grep_keys($pattern, $input, $flags = 0) {
return
array_intersect_key($input, array_flip(preg_grep($pattern, array_keys($input), $flags)));
}
?>
up
13
amolocaleb at gmail dot com
5 years ago
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 flawed
hom whitelisted
ashboard whitelisted
settings flawed
group whitelisted

I 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.

<?php
foreach($possibleUserInputs as $input)
{
if(
preg_grep("/^$input$/i",$whitelist)
{
echo
$input." whitelisted";
}else{
echo
$input." flawed";
}

}
?>
this results in:
homd flawed
hom flawed
ashboard flawed
settings flawed
group whitelisted
in_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
up
27
keithbluhm at gmail dot com
14 years ago
Run a match on the array's keys rather than the values:

<?php

function 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;
}

?>
up
-42
Timo Klemm
6 years ago
An even shorter way to run a match on the array's keys rather than the values:

<?php
function preg_grep_keys($pattern, $input, $flags = 0) {
return
array_flip( preg_grep($pattern, array_flip($input), $flags ) );
}
?>
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